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The Tree of Life
by Dana Visalli/www.methownaturalist.com
It is not known how life on earth began. Genetic and chemical evidence indicates that life was initiated only once, as one species, and that all succeeding organisms are descendants of this first life, which is
known as LUCA--the last universal common ancestor. The Earth is thought to be 4.5 billion years old,
and life appeared approximately 3.8 billion years ago, almost as soon as the planet had stabilized adequately for life to be theoretically possible. Estimates for the total number of species alive today vary
wildly, from around 5 million to more than 100 million. 1.8 million species have been named and categorized by scientists.
The immediate evolutionary relationships among organisms are not universally agreed upon and so
the branching of the Tree of Life has different interpretations. The one used here is one of the more
straightforward versions. Life began as relatively simple, single cells resembling Bacteria, and diversified
from there into 6 distinct Kingdoms: Bacteria, Archea, Protists, Plants, Fungi and Animals. A currently
popular alternate tree divides life first into 3 domains--Bacteria, Archea, and Eukaryotes (see below), and
then the Eukaryotes radiated into 4 kingdoms.
An important evolutionary division is between prokaryotes and eukaryotes. The word prokaryote
translates from the Greek as ‘before the seed,’ or ‘before the nucleus.’ Prokaryotes--Bacteria and Archea-do not have a nucleus in their cells--a separate area with its own membrane that contains the DNA of the
cell. The word eukaryote means ‘true seed’ or ‘true nucleus,’ and obviously a eukaryote does have a nucleus. This group includes the other 4 kingdoms of life besides Bacteria and Archea: Protists, Plants, Fungi and Animals.
Primary Life Groups: 6 Kingdoms:
Kingdom Bacteria
(Greek, ‘cane,’ because the first Bacteria discovered were rod-shaped)- About 2000
species known in 11 phyla. The total number is hard to assess, guesses range
from the tens of thousands to billions. Bacteria are prokaryotes; their cells have no
nucleus. They are found in almost all environments, from deep underground to
the stratosphere. The biomass of bacteria thought to exceed that of all animals and
plants combined. Bacterial cells are about 1/10th the size of eukaryotic cells and
are typically 0.5-5.0 u (micrometers; a micrometer is 1 millionth of a meter) in length.
Dana Visalli/[email protected]/www.methownaturalist.com,
Bacteria, magnified 1000x
Kingdom Archea
(Greek, ‘ancient’)- About 1000 species known in 2 phyla; the actual total existing
is unknown. Like Bacteria, Archea are prokaryotes, but they have unique properties that separate them from both eukaryotes and Bacteria. Most Archea are anaerobes--they obtain their energy without using oxygen, and in fact oxygen is
toxic to them. Many Archea are ‘extremeophiles,’ which means ‘lover of extreme
conditions.’ They can be found thriving in extremely hot water (up to and above
212°F), in ice, in super-saturated salt water. and deep below ground. Size is 0.1-15 u.
An Archea, Sulfolobus
Kingdom Protista
(Greek, ‘the very first’) (aka Protoctista)- 100,000-200,000 species in 36 phyla. Protists have eukaryotic cells and are mostly unicellular; some are multicellular but
have no specialized tissue, algae for example. They are typically divided into 3
groups, animal-like, plant-like and fungi-like protists. Size is variable; while averaging 0.1 mm, they vary from 0.01 mm to 65 meters (giant kelps).
Kingdom Plantae
(Latin, ‘to sprout’)- About 300,000 species in 12 phyla (often called divisions in the
Plant Kingdom). Plants are thought to have evolved from certain green algae.
They began to colonize land 450 million years ago, which required some means of
dealing the problem desiccation (drying out). Size ranges from the duckweed-like
Wolffia which is 0.5 mm long, to the largest redwood tree at 115 meters (380 feet)
tall.
Kingdom Fungi
(Greek ‘sponge’)- 75,000 species in 6 phyla have been identified; total may number more than a million. One of the 6 phyla of Fungi is lichens, which are mostly
fungal with an algae or cyanobacteria symbiont (lives inside the fungus). Fungi
are now thought to have diverged from other life 1.5 billion years ago, and colonized land about 500 million years ago. Most plant species have a symbiotic
(beneficial) relationship with one or more fungal species. The majority of the fungi that we see--mushrooms--have most of their organic structure underground
and can grow to enormous size. A honey mushroom (Armillaria ostoyae) in Oregon grows over 2200 acres and is a contender for the largest organism on the planet. Yeast cells can be as small as 2 micrometers (2 millionths of a meter).
Kingdom Animalia
(Latin, ‘breath’ or ‘soul’)- The total number of animals on earth is unknown; a million have been identified and the total is probably well over 5 million (including
insects and various worm phyla). 99% of all animals are invertebrates--they lack a
backbone. Of the 36 phyla of animals, most are aquatic worms of one sort or another. Truly land-dwelling forms are found only in two phyla, Arthropoda
(insects and their kin) and Cordata (animals with backbones). One contender for
the smallest animal in the world is the water bear or moss piglet (tardigrade); diminutive ones are 0.1 mm long. The largest animal in the world and the largest
that has ever lived is the blue whale. It can grow to 100 feet in length and 400,000
pounds. Before whaling there were probably a million blue whales in the oceans;
today there are about 8000.
Kingdoms break down as follows: Subkingdom, Class, Order, Family, Phylum, Genus, Species. For example humans are in Class Mammalia, Order Primates, Family
Hominidae, Genus Homo, Species H. sapiens.
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Paramecium, a Protist
Flower anthers & pollen
Honey mushroom
A moss piglet, in moss
A blue whale
Branches on the Tree of Life
Prions
(The name derived from ‘protein-infection’)-A prion is an infectious agent, a protein in a misfolded form. All known prion diseases in mammals affect the structure of the brain or other neural tissue and all are currently untreatable and fatal.
Diseases include bovine spongiform encephalapathy (mad cow disease) and
Creutzfeldt-Jacob Disease. Prions are not considered living organisms but are misfolded protein molecules which may propagate by transmitting a misfolded protein state. If a prion enters a healthy organism, it induces existing, properly
White spots are microscopic holes
folded proteins to convert into the disease-associated, misfolded prion form. This in neural tissue caused by prions
triggers a chain reaction that produces large amounts of the prion form. Prion replication is subject to natural selection just like in living organisms.
Viruses
(Latin, ‘poison’)- About 5000 viruses are known, with another 4000 unclassified,
and probably over million extant. A virus is a minute infectious agent that can
reproduce only by entering a host cell in a living organism and using its cell machinery. Some can crystallize like minerals and persist for years in that state. Viruses can infect all types of life forms, from animals and plants to Bacteria and
Archea. The smallest ones are only 20 nm (nanometers, 20 billionths of a meter, 20
millionths of a millimeter).
Viruses attacking a bacteria
The virus particle, or virion, in its simplest form is just nucleic acid enclosed in a protein shell. Its genome
may consist of double- or single-stranded DNA or RNA. the smallest viruses have as few as four genes, while
the largest have several hundred. Much smaller still are viroids, tiny molecules of naked RNA, which foul up
the metabolism of plants.
Prokaryotes
(Greek, ‘before the seed’) Prokaryotes are organisms that have what could be considered primitive cells
which have no nucleus--no membrane-bound area inside the cell containing the cell’s DNA. A second type of
larger cells, the eukaryotes (‘true seed’), do have a nucleus. Two kingdoms make up the prokaryotes, Bacteria
and Archea. They are the earliest life form we know of, 3.8 billion years old, and the only life-form on Earth
for 2 billion years. Prokaryotes outnumber all eukaryotes combined: there are more bacteria in one human
mouth than all the people that have ever lived; the human body contains more bacterial cells than human
cells, and it is thought that the biomass of Bacteria and Archea outweigh the combined biomass of the other 4
kingdoms. They are pervasive, being found in salty, acidic, alkaline, and very hot and cold environments as
well as what life typically considers comfortable.
Bacteria are essential to the other kingdoms, as decomposers of organic material, fixers of nitrogen, and producers of atmospheric oxygen and nitrogen. If Bacteria disappeared, the other four kingdoms would soon follow. On the other hand half of all human disease is caused by Bacteria. Some are opportunistic- they are
always present, for example Streptoccus pneumonia, which is always in the throat, and will multiply when
body defenses are down.
Prokaryotes are 1/10 to 1/100 the size of eukaryotic cells, have 1/1000 the DNA, and are haploid, which
means they only have one strand of DNA, rather than two (diploid). Bacterial motility (movement) is by
flagella or slime secretion. Reproduce occurs by binary fission--splitting in half--which progresses geometrically. Some cells can reproduce every 20 minutes, which would equal 1 million kg in 24 hrs. Like sex in eukaryotes, prokaryotes do indulge in bacterial conjugation, when two organisms come into contact, a thin
bridge can form, through which one of the bacteria donates a copy of some of its DNA. Many prokaryotes
can also pluck short strands of DNA out of the surrounding liquid medium, where it has been ejected by other cells.
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Kingdom Bacteria
Actinobacteria- Although known primarily as soil bacteria, they may be more
abundant in freshwaters. Actinobacteria is one of the dominant bacterial phyla
and contains one of the largest of bacterial genera, Streptomyces. While many
cause diseases in humans, Streptomyces is a notable source of antibiotics. Although some of the largest and most complex bacterial cells belong to the Actinobacteria, the group of marine bacteria in this phylum has been described as
possessing some of the smallest free-living cells.
Streptomyces
Aphragmabacteria- These are tiny, irregularly-lobed, ameba-like cells that live as intracellular parasites of
many different animals, plants, and protists. As such, they are the smallest cellular organisms on earth with a
range in size of 0.3-0.5 µm (micrometer, a thousandth of a millimeter). Several Aphragmabacteria diseases afflict humankind. One is Mycoplasma pneumoniae, the causative agent of a disease of the upper and lower respiratory tracts.
Bacteroides- Obligate anaerobes (cannot co-exist with oxygen). Bacteroides are normally mutualistic, making
up the most substantial portion of the mammalian gastrointestinal flora, where they play a fundamental role
in processing of complex molecules to simpler ones in the host intestine. As many as 1010-1011 (100 billion)
cells per gram of human feces have been reported. Studies indicate that long-term diet is strongly associated
with the gut microbiome composition. Those who eat plenty of protein and animal fats have predominantly
Bacteroides bacteria, while for those who consume more carbohydrates the Prevotella species dominate
Chlorobia- A strictly anaerobic (‘without oxygen’), photolithotrophic (‘rock-living’) green sulfur bacteria using hydrogen sulfide as an electron source (and sometimes hydrogen gas, and water) and CO2 as a carbon
source. Chlorobium species are thought to have played an important part in mass extinction events on Earth. If
the oceans turn anoxic (due to the shutdown of ocean circulation) then Chlorobium would be able to out-compete other photosynthetic life. They would produce huge quantities of methane and hydrogen sulfide which
would cause global warming and acid rain. This would have huge consequences for other oceanic organisms
and also for terrestrial organisms. Evidence for abundant Chlorobium populations is provided by chemical fossils found in sediments deposited at the Cretaceous mass extinction.
Chloroflexa- Another strictly anaerobic, photolithotrophic green sulfur bacteria recently split out of Chlorobia (above), found in hot springs.
Cyanobacteria (cyano is Greek for ‘blue’)- Aerobic (‘with oxygen’) photosynthesizers. By producing gaseous oxygen as a byproduct of photosynthesis, cyanobacteria are thought to have converted the early reducing (negatively charged)
atmosphere into an oxidizing one (positively charged, hungry for electrons,
which are negative.....and are readily available from hydrogen atoms), which dramatically changed the composition of life-forms on Earth by stimulating biodiversity and leading to the near-extinction of oxygen-intolerant organisms. According
Cyanobacteria
to endosymbiotic theory, the chloroplasts found in plants and eukaryotic algae
evolved from cyanobacterial ancestors via endosymbiosis....which is to say, chloroplasts were once individual,
free-living bacteria, which were engulfed by a larger bacteria, probably with an intention to consume, but instead of being consumed began to work together with and inside of the larger cell (symbiosis= ‘working together).
Deinococci (from the Greek, ‘dreadful granule’)- Aerobic bacteria that are highly
resistant to environmental hazards. Deinococcus survive when their DNA is exposed to high doses of gamma and UV radiation. Where other bacteria change
their structure in the presence of radiation, such as endospores, Deinococcus tolerate it without changing their cellular form and do not retreat into a hardened
structure. A human lethal dose of radiation is 500 rads, Deinococcus has tolerated
3 million rads. Found in hot springs.
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Deinococcus
Pirellulae- Obligate aerobes found in fresh water. Species in this phylum cause a number of diseases, including chlamydia and pneumonia.
Proteobacteria- Purple bacteria- Because of the great diversity of forms found in this group, the Proteobacteria are named after Proteus, a Greek god of the sea capable of assuming many different shapes. They include
a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and Yersinia, and many other
notable genera. Others are free-living (nonparasitic), and include many of the bacteria responsible for nitrogen fixation.
Spirochaetae- A group of chemoheterotrophs (they feed on energy bound up in compounds) with helically
coiled (corkscrew shaped) cells. Most are free-living and anaerobic, but there are numerous exceptions.
Found in marine and fresh water, muddy sediments, and the gastrointestinal tracts of some mammals.
Thermotogae (Greek ‘heat’ and ‘toga’-some species have an extra sheath)- anaerobic, mostly thermophilic
(heat loving) and hyperthermophilic bacteria found around deep sea vents and hot springs.
Kingdom Archea
It was realized only as recently as the 1970s that Archaea as organisms have
unique properties separating them from both Bacteria and all of the eukaryotes.
Archea are similar in size and shape to Bacteria, but contain genes and chemical
pathways that are more closely related to eukaryotes than to Bacteria. Most are
‘extremophiles,’ living in extreme environments: hot, cold, salty, dark, although
they have also been found in benign environments, like in the human navel.
Archea
Crenarchaeota (Greek, ‘spring old quality’)- Thermoacidophiles, Crenarchaeota
inhabit hot springs all over the world, and also may be abundant in deep in rocks. They are autotrophs that
assimilate CO2 into their bodies using inorganic chemicals as energy sources: H2, CH4, NH3, and other reduced (hydrogen rich) compounds.
Euryarchaeota (Greek, ‘true ancient ones’)- Methanogens and halophiles (salt-loving)- some are motile via
flagella and some are immotile. All 3 classic bacterial shapes-- rods, spirillum and coccus-- are represented.
Methanogens are found worldwide in sewage, sediments, and in the intestinal tracts of animals, including
wood-eating insects. They have names prefixed by ‘methano.’ Methanogens obtain energy by reducing CO2
and oxidizing H2, forming methane. Halophiles live in extremely salty or alkaline environments.
Kingdom Protista
(Greek ‘very first to establish’)- The protists are generally speaking the smallest of the organisms with eukaryotic cells--that is, cells with a nuclear membrane (forming the nucleus) inside the larger cell membrane. Most
protists are single-celled organisms. The kingdom as a whole is a catch-all unit that has in other schemes been
divided up in to as many as 20 kingdoms. Used here is one of the most basic and easily understood taxonomies for this group. The 16 phyla listed are divided into 5 informal groups based on mobility and nutrition:
Group 1-Heterotrophs with no permanent means of locomotion (3 phyla):
Actinopoda (Greek, ‘ray feet’)- Actinopods and radiolarians are non-motile, heterotrophic Protista with a diameter of 0.1–2 mm that produce intricate mineral
skeletons made of silica. They are found as zooplankton throughout the ocean,
and their skeletal remains make up a large part of the ocean floor as siliceous
ooze. Radiolarians have many needle-like pseudopodia (‘false feet’) which aid in
the Radiolarian's buoyancy. Radiolarians can often contain symbiotic algae which
provide most of the cell's energy. The earliest known Radiolaria date to the very
A Radiolarian
start of the Cambrian period 550 million years ago. Radiolaria appear to be most
abundant in warm waters of the equatorial zone, unlike diatoms which prefer cool water. They can also act as
predators, capturing diatoms and other organisms by ingesting them into their central cavity.
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Foraminifera (Latin, ‘little hole bearing’)- There are about 9000 known species.
Foramins are amoeboid protists, characterized by streaming protoplasm that
among other things is used for for catching food, and by an by an external shell, or
test, usually made of calcium carbonate. All but a few are aquatic and most are
marine, the majority of which live on or within the seafloor sediment (benthos)
while a smaller variety are floaters in the water column at various depths
(plankton). A few are known from freshwater or brackish conditions and some soil
species have been identified. Foraminifera typically produce a shell which can have
either one or multiple chambers, some becoming quite elaborate in structure. They
are usually less than 1 mm in size, but some are much larger, the largest species
reaching up to 20 cm.
Rhizopoda (Greek, ‘root foot’)- the single-celled amoebas. They are characterized
by the possession of pseudopodia--temporary outgrowths of the cell wall, which
are used for locomotion and engulfing food particles. Rhizopods are found in freshwater and marine habitats and the soil. Amoebas reproduce by binary fission; there
is no sexual reproduction. Amoeboid-like cells occur not only among the protozoa,
but also fungi, algae and animals.
A foraminfera test (shell)
Amoeba
Group 2- Photosynthetic Protists (7 phyla)
Bacillariophyta (Latin, ‘little stick plant’)- Diatoms (Greek, ‘to cut through,’ referring to the 2 halves of the diatom’s shell) are a major group of algae, and are among
the most common types of phytoplankton. Most diatoms are unicellular, although
they can exist as colonies in the shape of filaments or ribbons, fans, zigzags, or stars.
Diatoms are major producers within the marine and freshwater food chains. A
unique feature of diatom cells is that they are enclosed within a cell wall made of
silica. They are especially important in oceans, where they are estimated to contribute up to 45% of the total oceanic primary production, and are responsible for 25% of the
oxygen in the atmosphere.
Chlorophyta (Greek, ‘yellow-green plant’)- These are the green algae. They have
traits in common with the plants (like plants they utilized chlorophylls ‘a’ and ‘b’,
and store energy as starch) and are in fact sometimes placed in the Plant Kingdom.
Green algae may be unicellular (one cell), multicellular (many cells working together), colonial (living as a loose aggregation of cells) or coenocytic (composed of one
large cell without cross-walls). While most species live in freshwater habitats and a
large number in marine habitats, other species are adapted to a wide range of environments. Watermelon snow, or Chlamydomonas nivalis, lives on summer alpine
snowfields. Others live attached to rocks or woody parts of trees. Some lichens are
symbiotic relationships between fungi and green algae. Life was simple when all
green-colored algae were included in a single phylum. Increasingly, it has become
clear that the green algae are very diverse in their relationships and are now often
included in two phyla, Chlorophyta (4500 species) and Charophyta (3500 species).
Diatom-Cymbella affinis
Volvox aureas
Synura- a Chrysophyta
Chrysophyta (Greek, ‘golden plant’)- A phylum of unicellular marine and freshwater protists known as the golden algae, this includes the abundant coccolithophores
and sometimes the diatoms (Bacillariophyta). Some are free-swimming individuals
and others are colonial; the vast majority are photosynthetic. As such, they are particularly important in lakes, where they may be the primary source of food for zooplankton. They are not considered truly autotrophic by some biologists because
nearly all chrysophytes become facultatively heterotrophic (‘other-feeding’) in the
absence of adequate light, or in the presence of plentiful dissolved food. When this
occurs, the photosynthetic cell atrophies and the alga may turn predator, feeding on
bacteria or diatoms. There are more than 1000 described species.
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Coccolith- Emiliania huxleyi
Dinoflagellata- (Greek, ‘whirling whip’)- A large group of flagellated (tailed) protists. Most are marine plankton, but they are common in freshwater habitats as
well. Many are photosynthetic, but some are known to be mixotrophic, combining
photosynthesis with ingestion of prey. In terms of number of species, dinoflagellates form one of the largest groups of marine eukaryotes, although this group is
substantially smaller than the diatoms. Some species are endosymbionts of marine
animals and play an important part in the biology of coral reefs. About 1600 species are described, with an estimate of 2600 total extant. So-called red tides are
caused by dinoflagellates.
Dinoflagella
Euglenophyta- Euglenids are commonly found in freshwater, especially when it is rich in organic materials,
with a few marine, and endosymbiotic members. Most euglenids are unicellular. Many euglenids have chloroplasts and produce energy through photosynthesis, but others feed by phagocytosis (‘to devour a cell’) or
strictly by diffusion. Prey such as bacteria and smaller flagellates are ingested through the cell mouth (the cytosome).
Phaeophyta (Greek, ‘dusky brown plant’)- Brown Algae, a large group of mostly marine multicellular algae,
including many seaweeds of colder Northern Hemisphere waters. They play an important role in marine environments, both as food and for the habitats they form. For instance Macrocystis, a brown kelp, may reach 60
meters in length, and forms prominent underwater forests. Worldwide there are 1500–2000 species.
Rhodophyta (Greek, ‘red plant’)- Red Algae, about 6000 species of mostly multicellular algae, primarily marine but including 164 freshwater species. Many of the coralline algae, which secrete calcium carbonate and
play a major role in building coral reefs, belong here.
Group 3- Heterotrophs with flagella or cilia (2 phyla)
Ciliophora (Latin, ‘eyelash bearing’)- The ciliates are a group of protists characterized by the presence of hair-like organelles called cilia, which propel the organism
via an undulating movement. Ciliates are an important group of protists, common
almost everywhere there is water: in lakes, ponds, oceans, rivers, and soils. About
3,500 species have been described, and the potential number of extant species is
estimated at 30,000. Included in this number are many ectosymbiotic and endosymbiotic species, as well as some obligate and opportunistic parasites. Ciliate spe- Didinium injesting a Paramecium
cies range in size from as little as 10 µm to as much as 4 mm in length, and include
some of the most morphologically complex protists. Most ciliates are heterotrophs, feeding on smaller organisms, such as bacteria and algae, and detritus swept into the oral groove (mouth) by modified oral cilia.
Zoomastigophra (Greek, ‘animal whip’)- These are free living or parasitic, sexual or asexual heteroptrophs
with at least one flagellum; some have thousands of them. Some species are parasitic, such as Typanosoma, a
zooflagellate causing African Sleeping Sickness. The protist disease agents are acquired from human beings
or from animals harboring the parasites.
Group 4- Non-motile spore-forming animal parasites (1 phylum)
Apicomplexa (Latin, ‘summit enfolding’) (aka Archeaprotista)- Apicomplexa is a
large group of parasitic protists, most of which possess a unique organelle, a type
of plastid called an apicoplast, and an apical structure involved in penetrating a
host's cell. They are unicellular, spore-forming, and exclusively parasites of animals. Flagella are found only in the motile gamete. Includes Plasmodium, the cause
of malaria, which kills up to 200 million people per year, and Giardia lamblia, the
causative agent of giardia.
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Giardia lamblia
Group 5- Slime Molds-heterotrophs with restricted mobility
Acrasiomycota (Greek, ‘bad judgement fungus’) (aka Rhizopoda)- Cellular slime
molds; they occur in damp habitats on land and feed on microorganisms. When
food runs out and they are ready to form sporangia, they release signal molecules
into their environment, by which they find each other and create swarms. These
amoeba then join up into a tiny multicellular slug-like coordinated creature, which
crawls to an open lit place and grows into a fruiting body, a sporangium. Some of
the amoebae become spores to begin the next generation, but some of the amoebae
sacrifice themselves to become a dead stalk, lifting the spores up into the air.
Myxomycota (Greek, ‘mucus fungus’)- Plasmodial slime molds share one big cell
wall that surrounds thousands or millions of nuclei. Proteins called microfilaments
act like tiny muscles that enable the mass to crawl at rates of about 1/25th of an
inch per hour. As long as there is enough food and moisture, the mass thrives. But
when food and water are scarce, the mass separates into smaller blobs. The Plasmodium forms stalks topped by sphere-like fruiting bodies that contain spores that are
carried by the rain or wind to new locations.
Cellular Slime Mold
Plasmodial Slime Mold
Oomycota (Greek, ‘egg fungus’)- filamentous protists which must absorb their food from the surrounding
water or soil, or may invade the body of another organism to feed. As such, oomycetes play an important role
in the decomposition and recycling of decaying matter. Parasitic species have caused much human suffering
through destruction of crops and fish. ‘Egg fungus’ and refers to the large round oogonia, or structures containing the female gametes. The Oomycota were once classified as fungi, because of their filamentous growth,
and because they feed on decaying matter like fungi. The cell wall of oomycetes, however, is not composed of
chitin, as in the fungi, but is made up of a mix of cellulosic compounds. Some water molds are parasites on
other organisms; they may grow on the scales or eggs of fish, or on amphibians. Other species are parasitic on
aquatic invertebrates such as rotifers, nematodes, and arthropods, and on diatoms.
Kingdom Fungi
(From Greek, ‘sponge’)- There are an estimated 100,000 species. Fungi differ from other organisms in having
cell walls that contain chitin; genetic studies have shown that fungi are more closely related to animals than to
plants. Nearly all fungi can reproduce asexually by releasing spores produced by a single parent. Many are
also capable of sexual reproduction by conjugation of tissue. For many, sexual reproduction is a contingency
mode that occurs only when there has been an unfavorable change in the environment. The few unicellular
fungi, like yeast, are thought to have evolved from multicellular forms. Mycelium (the underground portion
of the organism) can grow up to half a mile a day. The oldest fossil fungi date to the Devonian, 410 million
years ago. These fossils are intimately associated with fossil plant tissue. It has been suggested that fungal associations made it possible for plants to become truly terrestrial. Today terrestrial ecosystems would collapse
without fungi to decompose dead organic matter. 8 genera in this classification:
Ascomycota (Greek, ‘bladder fungus’)- About 64,000 species known. The sac-fungi
produce spores in small cup-shaped sacs called asci, hence the name Ascomycota.
The mature sac fungi spores are known as ascospores, they are released at the tip of
the ascus breaks open. Yeast is the most common one-celled ascomycete. Yeast reproduces through asexual process called budding. The buds form at the side of the
parent cell, they pinch-off and grow into new yeast cell which is identical to the parent cell. Examples of sac-fungi are morels, truffles, cup fungi and powdery mildews.
Morels are Ascomycetes
Basidiomycota (Greek, ‘club fungus’)- About 32,000 species known. Basidiomycota includes the classsic mushrooms, puffballs, smuts, and rusts. The spores are borne on a club-shaped spore case called basidium. The ba8
sidia are lined up on the gills under the cap. An average sized mushroom produces
over 16 billion spores. These spores rarely germinate or mature.
Blastocladiomycota- These small fungi live in fresh water and soil. Some are parasites on nematodes, midges, crustaceans and plants, including one that causes
‘brown spot disease’ on corn, and another that parasitizes alfalfa.
Amanitas are Basidiomycetes
Chytridiomycota (Greek, ‘little cooking pot fungus’)- Chytrids are one of the early diverging fungal lineages
and are saprobic, degrading refractory materials such as chitin and keratin, or acting as parasites. Their membership in kingdom Fungi is demonstrated by their chitin cell walls and absorptive (saphrophitic) nutrition.
About 800 species have been identified. Chytrids have been isolated from a variety of aquatic habitats, including peats, bogs, rivers, ponds, springs, and ditches, and terrestrial habitats, such as acidic soils, alkaline soils,
temperate forest soils, rainforest soils, arctic and Antarctic soils. The chytrid species Batrachochytrium dendrobatidis is responsible for chytridiomycosis, a disease of amphibians. Discovered in 1998, this disease is known to
kill amphibians in large numbers, and has been suggested as a principal cause for the worldwide amphibian
decline.
Glomeromycota- Approximately 230 described species. Most species are terrestrial and widely distributed in
soils worldwide where they form symbioses (mycorrhizas) with the roots of the majority of plant species
(>80%).
Lichenes (Lichenales)- A lichen is a composite organism that emerges from algae
or cyanobacteria (or both) living among filaments of a fungus in a mutually beneficial relationship. The whole combined has properties that are very different from
properties of its component organisms. The fungus benefits from the symbiotic relationship because algae or cyanobacteria produce food used by the fungus by photosynthesis. There are about 20,000 known species of lichens.
Xanthoria- a crustose lichen
Micosporidia- The microsporidia constitute a phylum of spore-forming unicellular parasites. They were once
thought to be protists but are now known to be fungi. Loosely 1500 of the probably more than one million species are named. Microsporidia are restricted to animal hosts, and all major groups of animals host microsporidia. Most infect insects, but they are also responsible for common diseases of crustaceans and fish.
Zygomycota- These fungi are usually found on cheese, bread, and other decaying
food. They are zygote forming fungi, hence the name zygomycota. The spores are
produced in round-shaped case called sporangium. The grayish fuzz seen on bread
and decaying food is actually mass of mature sporangia mold. Under the microscope they are seen as pinheads. When the sporangium breaks open hundreds of
spores are released. About 700 species are known.
Zygomycota sporophytes
Kingdom Animalia
(Latin ‘having breath’)- All animals are heterotrophs (‘other-eating’) and must ingest other organisms or their
products for sustenance. Most animal phyla appeared in the fossil record as marine species during the Cambrian explosion 540 million years ago. The earliest known animal fossils are found in 665-million-year-old
rock in Australia. They are distinguished from plants, algae and fungi by lacking rigid cell walls and digesting food in an internal chamber. All animals are motile, if only at certain life stages.
Subkingdom Parazoa (Greek, ‘beside animals’): lack tissues organized into organs and have an indeterminate shape.
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1. Placozoa (Greek, ‘flat animal’): These are considered ‘basal animals,’ representatives of early evolution of the Animal Kingdom. They are the simplest in structure of
all non-parasitic animals. They are generally classified as a single species, Trichoplax
adhaerens, although there is enough genetic diversity that it is likely that there are
multiple, morphologically similar species. They were first discovered in 1883, in a
saltwater aquarium in Austria. Barely visible to the naked eye at about 1 mm across,
they are amoeba-like, with no regular body outline. It feeds on small particles of A Placozoan, probably Trichoplax
organic debris. It’s evolutionary history is not clear and it is considered possible they
lost physiological complexity rather than never having had it.
2. Porifera (Latin, ‘pore bearing’): 10,000 species, most marine with only 150 species
in freshwater. These are the ‘sponges,’ multicellular organisms that have bodies full
of pores and channels allowing water to circulate through them. Sponges do not
have nervous, digestive or circulatory systems. Instead most rely on maintaining a
constant water flow through their bodies to obtain food and oxygen and to remove
wastes. They are filter feeders; it is estimated that a sponge must filter 1 ton of water
Porifera
to grow 1 ounce in weight. Most are hermaphrodites; sperm is released into water
and drawn into neighboring sponge. Sponges are similar to other animals in that they are multicellular,
heterotrophic, lack cell walls and produce sperm cells. Unlike other animals, they lack true tissues and organs and have no body symmetry.
Subkingdom Eumetazoa (Greek, ‘true large animals): Eumetazoa have tissues organized into organs. They
are divided into two branches, Radiata (radial body symmetry) and Bilaterata (bilateral symmetry).
Radiata:
3. Cnidaria (pronounced nigh-dear-ee-ah, Greek, ‘nettle’) (aka Coelenterata) (Greek,
‘hollow intestine’) >10,000 species, including hydras, jellyfish, sea anenomes, and
coral. They have one body opening, a gastrovascular cavity, with no distinct organs. There are two body plans, a sessile polyp (e.g. hydra) and a floating medusa (jellyfish). They are all carnivores, with a nerve net but no brain; their behavior
is rigid. No one has yet trained a jellyfish. Some jellyfish have tentacles are 30 meters long. Fossils exist to 700 million years age. Divided into 4 classes:
Pacific Sea Nettle- Cnidaria
1. Anthozoa: Almost wholly sessile: sea anemones and coral animals. 6200 sp.
2. Cubozoa: Sea wasps and box jellies. A few genera.
3. Hydrozoa: Includes hydras and ‘colonial swimmers’ such as the Portugese Man o’ War; 3 100 sp.
4. Scyphozoa: jellyfish. 200 sp.
4. Ctenophora (Greek, ‘comb bearing’): Comb Jellies. About 150 species known.
Body of soft gelatinous material in a membrane bag, with comb paddles, which are
aggregates of external cilia. All are marine. They range in size from a few millimeters to 1.5 meters in length. Like Cnidarians they have a decentralized nerve net
rather than a brain; they are sometimes classified with Cnidarians in the now usually defunct phylum Coelenterata. Ctenophores are predators, taking prey ranging
from microscopic larvae and rotifers to the adults of small crustaceans.
A Ctenophoran
Bilateral Symmetry
Bilaterally symmetrical organisms may be acoelomate (Greek,‘without a hollow’--no cavity between gut and
outer body wall), pseudocoelomate (cavity present, but not completely lined with mesoderm), or coelomate
(having a true coelom, a body cavity completely lined with mesoderm).
Acoelomate- no cavity between gut and outer body wall
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5. Platyhelminthes (Greek, ‘flat worm’): 15,000 species. Relatively simple bilateral,
unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates (no body cavity), and have no specialized circulatory and respiratory organs,
which restricts them to having flattened shapes that allow oxygen and nutrients to
pass through their bodies by diffusion. The digestive cavity has only one opening
for both ingestion and egesetion (removal of wastes). Found in freshwater, marine
and humid terrestrial environments. Traditionally broken down into the 3 following A Flatworm, Platyhelminthes
groups, which have proven to not be monophyletic (do not share a close common ancestor):
Cestoda: parasitic tapeworms, living mostly on vertebrates. No digestive system. Can grow to more than 20
meters.
Trematoda: parasitic flukes, mostly on vertebrates. There are 200 million people around the world who are
infected w blood flukes (schistoma), suffering body pains, anemia and dysentery.
Turbellaria: free-living flatworms. Simplest of all Bilateria, the are acoelomate with one body opening, distinct organs, and a rudimentary; they can modify response to stimuli.
6. Nematomorpha (Greek, ‘thread-form’)- 350 species are known and 2000 are expected. They are known as horsehair worms, so-called because they are hair-like
and there was a belief they sprang from horsehairs. They range in size from 50-100
cm. They are found all over the world in all kinds of water, a few are found in soil.
They have no respiratory, circulatory, excretory nor digestive organs, absorbing nutrients through the cell walls. The adult worms are free-living, but the larvae are
parasitic on arthropods such as beetles and grasshoppers.
Horsehair Worm
7. Nemertina (Greek, the name of a sea nymph)- About 900 species. ranging in size from 0.5 mm to one that
measured 54 meters, making it the longest animal ever found. Know in the vernacular as proboscis worms,
also called ribbon worms. The are free-living, mostly bottom-dwelling marine worms with a distinctive eversible proboscis consisting of a long, hollow tube. Nemerteans move slowly, using their external cilia to glide on
surfaces on a trail of slime. They are very similar to flatworms, but do have a digestive tube with two openings and simple circulatory system.
Pseudocoelomate-an incipient cavity between the gut and the outer body
8. Nematoda Greek, ‘thread’)- About 25,000 species described, an estimated 1 million in existence. Nematodes or roundworms, more than half are parasitic. Unlike
cnidarians and flatworms, nematodes have tubular digestive systems with openings
at both ends. They are present in nearly every ecosystem from marine to freshwater
to to soils. They represent 90% of all animals on the ocean floor, and are so numerous that they may comprise 80% of all individual animals on earth. Humans host at
least 50 species of nematodes. Nematodes are critical in the aeration of soil and the
circulation of its mineral and organic components.
9. Rotifera (Latin, ‘wheel bearer’)- 2200 species have been described. Most rotifers
are 0.1-0,5 mm long, and are common in freshwater environments throughout the
world, with a few saltwater species. Some rotifers are free swimming and truly
planktonic, others move by inchworming along a substrate, and some are sessile,
attached to gelatinous holdfasts that are attached to a substrate. The are an important part of the freshwater zooplankton, being a major food source and with many
species also contributing to the decomposition of soil organic matter.
10. Acanthocephala (Greek, ‘thorn head’)- 1150 species have been described. A
phylum of parasitic worms known as thorny-head worms, characterized by the
presence of an eversible proboscis armed with spines, which it uses to pierce and
hold the gut wall of its hosts, which may include invertebrates, fishes, amphibians,
birds and mammals. Recent genome analysis has shown they are descended from
rotifers.
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Nematode
Rotifer
Acanthocephala
11. Kinorhyncha (Greek, ‘to move the snout’) - 180 species known. A phylum of
small (1 mm or less) marine invertebrates that are widespread in mud aand sand at
all depths; sometimes called mud dragons. They do not have external cilia, but instead have a number of spines along the body, plus up to 7 circles of spine around
the head. These are used for locomotion, gripping the substrate with the spines
while drawing up the body. They feed on organic matter in the substrate.
Kinorhyncha
12. Annelida (Latin, ‘little ring’)- 10,000 species of worms, distinguished by the ringlike external segments
that coincide with internal partitions containing digestive and reproductive organs repeated in tandem. They
live in marine and freshwater and in soil, ranging in size from 0.5 mm to 3 meters (the giant Australian earthworm). Included here are the former phyla Echiura (240 species of small marine worms), Pogonophora (deepsea tube worms, 80 species) and Sipuncula (peanut worms, also marine, 300 species). There are 3 classes of Annelids:
Hirudinea: Leeches, 300 species. Leeches can suck up to 10 times their body weight of blood,then not eat
again for 4 months.
Oligochaeta: 3100 species. Terrestrial bristle worms, including earthworms.
Polychaeta (‘many setae’ or bristles”) 5400 species. Marine bristle worms, featherduster worms, tubeworms.
13. Onychophora (Greek, ‘claw bearers’)- 180 species. Popularly known as velvet
worms, these creatures have tiny eyes, antennae, and multiple pairs of legs
(between 13 and 43 pairs). Velvet worms grow to between 0.5 and 20 cm long. They
have variously been compared to worms with legs, caterpillars and slugs. Most
common in tropical regions of the Southern Hemisphere, they prey on smaller animals such as insects, which they catch by squirting an adhesive mucus. In modern
Onychophora
zoology, they are particularly renowned for their curious mating behavior and for
bearing live young. Males of many Australian species exhibit special structures on the head, which apparently
take over certain tasks in transferring sperm to the females. In the species Euperipatoides rowelli, sperm is
collected by these structures, and, when a female is encountered, the worm inserts its head in the vagina.
14. Tardigrada (Latin, ‘slow step’)- More than 1000 species. The common names for
Tardigrades are ‘moss piglets’ (they are common among moss) and ‘water bears’
(tardigrades have legs tipped with claws, and a lumbering gait). They are microscopic, water-dwelling, segmented animals with eight legs. Depending on the species, they range in size from 0.1 to 1.5 mm long. Tardigrades occur throughout the
world in some of the most inhospitable places, from high peaks in the Himalayas
(above 20,000 ft) to boiling water near heat vents on the ocean floor, and from the
A Moss Piglet
Arctic tundra to vast ice fields of Antarctica. During severe environmental conditions that would kill most
creatures on earth, tardigrades roll up into little dehydrated balls called "tuns" where they survive for extended periods of time. This dormancy phenomenon is called cryptobiosis (or anabiosis). They can survive temperatures of -450° F to +300°F. A lethal dose of x-rays for humans is 500 roentgens; it is 600,000 roentgens for
moss piglets.
15. Bryozoa (Latin, ‘moss animal’)- 4150 species known. Aquatic invertebrate filter
feeders because they often look like plants. Typically about 0.5 mm long, they sieve
food particles out of the water using a retractable crown of tentacles lined with cilia.
Mostly marine, some live in freshwater. Some species form mineralized exoskeletons that encrust over surfaces.
Coelomate: has a true body cavity completely lined with mesoderm.
A Bryozoan
16. Brachiopoda (Latin, ‘arm foot’)- 300 species. Marine animals with bivalve shells that attach to rocks by a
fleshy stalk.. They have the common name lamp shells, because some look like old pottery oil lamps. Brachio12
pods live mostly in cold water and low light. They can live up to 30 years; most obtain a width of only 10 to 30 mm. The ventral shell is is usually larger than the dorsal,
and the body is aligned within differently than in mollusks (dorsally and ventrally
rather than laterally).
17. Mollusca (Latin, ‘soft’)- 150,000 species, including snails slugs, oysters, clams, ocA Brachiopod
topi, and chitins. Most are marine while some live in freshwater or are terrestrial. All
are soft-bodied, most are protected by a shell of calcium carbonate. Size ranges from 1 mm to 20 meters (giant
squid). North America has the largest number of freshwater mollusk species in the world. There are 5 common classes (and 3 rare ones not listed here):
1. Cephalopoda (head foot’)- Octopi, squid and nautilus. They are built for speed,
with well-developed brains. Shelled cephalopods called ammonites were the dominant invertebrate predators for hundreds of millions of years until the mass extinction at the end of the Cretaceous. Only one shelled cephalopod survives, the
chambered nautilus.
2. Gastropoda (‘stomach foot’)- snails and slugs, 100,000 species. The largest of all
Chambered Nautilus
classes except Insecta (below).
3. Pelecyoda (‘hatchet foot’)- Also known as Bivalva: clams, mussels, scallops, oysters (15,000 species).
4. Polyplacophora- Chitons. They have oval bodies covered by eight scaly plates (650 species).
5. Scaphopoda- Tusk or tooth shells.
18. Chaetognatha (Greek, ‘hair jaw’)- About 125 species identified, commonly
known as arrow worms. A phylum of predatory marine worms that are a major
component of plankton worldwide. They are found in all marine waters, from shallow tide pools to the deep sea and polar regions. Most chaetognaths are transparent
and are torpedo shaped, but some deep-sea species are orange. They range in size
from 2 mm to 12 cm. Despite the limited diversity of species, the number of individuals is large.
Jaws of Chaetognatha
19. Arthropoda (Greek, ‘jointed foot’). Probably 5 million species or many more; the total is unknown. As biologist JBS Haldane famously remarked, ‘God has an inordinate fondness for beetles.’ Some taxonomies break
up Arthropoda into Chelicerata--spiders & their kin, and Mandibulata-insects and crustaceans. Arthropods
have jointed appendages and an exoskeleton made of chitin (a stiff and complex derivative of glucose). They
have well-developed sense organs, extensive cephalization, and an open circulatory system (no arteries and
veins). The exoskeletons, which evolved in the sea for protection, pre-adapted arthropods for life on land, as
the chitin retains water. The oldest animal fossils found on land are 400 million year old millipedes. It is a
complex phylum, with 3 (or more) subphyla) and 18 classes.
Subphylum Chelicerata (Greek, ‘arm lips’)- Spiders & Kin. 6 pair of appendages, of
which the first pair differ from the others. Called chelicerae, they are jawlike and
grasping. Chelicerata lack sensory antennae. 3 classes:
1. Class Arachnida: Spiders, scorpions, mites and ticks. All have 4 pair of segmented
legs, most are carnivorous, most prey on insects. There are 10 or more orders, 8 are
listed below.
1. Acarina- mites and ticks- 48,000 species.
2. Araneida-spiders- 38,000 named, may be twice as many extant.
3. Chelonethida- pseudoscorpions- 3300 species.
4. Hydrocarina-watermites- 5000 species.
5. Phalangida- daddy longlegs.
6. Scorpoionida- scorpions- 1300 species.
7. Solpugida- wind scorpions- 200 species.
8. Thelyphonida- whip scorpions- 100+ species.
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umping Spider
Whip Scorpion
2. Class Merostomata- Horseshoe crabs- 4 species.
3. Class Pycnogonida- Sea spiders- 1300 species.
Subphylum Crustacea (Latin, ‘skin’)- 68,000 species described, includes shrimp, copepods, isopods, barnacles, krill, crabs, lobster. Crustaceans have 2 antennae and 2
body regions, the cephalothorax and the abdomen. There are 9 orders:
1. Amphipoda (‘both feet’)- scuds and beach hoppers.
2. Branchiopoda- fairy shrimp, tadpole shrimp, clam shrimp.
3. Cirripedia- barnacles.
Copepod
4. Cladocera- water fleas.
5. Copepoda- copepods. Among the most numerous of animals.
6. Decapoda- lobster, crayfish, crabs, shrimp.
7. Isopoda (‘equal feet’)- 7 pair of equal leglike appendages. Mostly marine but includes sow & pill bugs.
8. Malacostraca- krill.
9. Ostracoda- seed shrimp.
Subphylum Hexapoda (or Uniramia)- Insects (Latin, ‘to cut into,’ referring to the distinct body segments)- Millions of species in at least 26 orders. Insects have 3 pairs of
legs, 3 body sections, 1 pair of antennae, and generally 1 or 2 pair of wings. In terms
of species diversity insects outnumber all other forms of life combined. Common on
land and in freshwater, they are rare in the sea. The fossil insects are from the Devonian, 410 million years ago.
Insecta
Subphylum Myriapoda- Centipedes and Millipedes. 14,000 species. Centipedes have 1 pair of legs per segment and antennae with 14 segments; they are terrestrial carnivores. Millipedes have 2 pair of legs per segment and antennae with 7 segments, they are vegetarian and detrivores. The millipede Illacme plenipes has
750 legs.
20. Echinodermata (Greek, ‘hedgehog skin’)- 7000 species. Starfish, sea urchins, sand dollars, sea cucumbers,
sea lilies. Adults have radial symmetry, but larvae are bilateral. There are no freshwater nor terrestrial species. They are characterized by the presence of tube feet, which serve for locomotion, food handling and respiration. Another distinct trait which most echinoderms have is their remarkable powers of regeneration of
tissue, organs, limbs, and in some cases complete regeneration from a single limb. Geologically they are important in that their ossified skeletons are major contributors to many limestone formations.
21. Hemichordata (Greek, ‘half chord’)- 90 species, known as acorn worms. They
are worm-like marine filter feeders from 2.5 to 250 cm long that inhabit U-shaped
burrows in sandy or muddy substrate. They resemble chordates in that they have
gill slits and a nerve chord, and they are in fact the closest extant phylogenetic reletives of chordaes among the invertebrates.
An Acorn Worm
22. Chordata (Latin, ‘chord’)- 65,000 species. All chordates share 3 distinct characteristics: 1. A notochord is present in all chordate embryos, 2. All chordates have dorsal, hollow nerve chord, 3.
Pharyngeal slits (gill slits) are present on all embryos (these probably originally functioned as filters for filter
feeding in early chordates). There are 3 subphyla:
1. Urochordata- 1260 species, these are the tunicates, in which most adults are softbodied, sessile or planktonic marine filter-feeders that lack the definitive chordate
features. However all tunicate larvae have the standard chordate features, including
long, tadpole-like tails; they also have rudimentary brains.
2. Cephalocordata (Latin, ‘head chord’)- 25 species, known as lancelet or amphioxus.
They are small marine animals with elongated bodies with a notochord that extends
Tunicate
the length of the body. They spend much of their lives buried in sand in shallow wa-
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ter, filter-feeding on organic matter through their 100 pharyngeal slits. In some locations they are extremely common; at Discovery Bay in Jamaica up to 5000
individuals can be found per square meter of sand.
3. Vertebrata- vertebrates with distinct skulls 64,000 species, including fish, amphibians, reptiles, mammals, and birds (this subphylum is sometimes referred to Craniata). Characteristics include 1. cephalization (a central brain and sensory structures,
A lancelet
2. a vertebral column enclosing a nerve chord, 3. a closed circulatory system with a
heart and veins, 4. paired appendages. Most vertebrate species survive an average of 2 million years before
going extinct. 7 existing classes and 2 extinct ones listed below.
1. Class Agnatha (‘without jaws’): 6 species; lampreys, hagfish and slime eels. No
true jaws, scales or fins. The vertebral column is cartilaginous. The young lamprey
ammocoete is similar to the amphioxus, with more apparent cephalization, larger
gill slits, mouth and segmented muscle. Included here are the extinct Ostracoderms
(shell-skinned), the first well defined vertebrates. They were small jawless, bony,
armored fish appearing in the Ordovician, abundant in the Silurian-Devonian.
The hard 'shell' over the head was of calcium phosphate, the equivalent of
bone. 2 orders:
1. Mxyiniformes: hagfishes.
2. Petromyzontiformes: lampreys.
Lamprey
2. Class Placoderma (‘plate–skinned’): A long extinct group of armored fish with jaws, which replaced the ostracoderms in the Devonian. Probable ancestors of the Chondrichthyes (bony fish). To 3 meters length.
3. Class Acanthodii: Appeared in the Devonian and now long-extinct, they were small (minnow-sized)
predators with spine–supported fins, body scales, jaws with replacement teeth and an operculum. They
are in an evolutionary line with Osteichthyes, both having homocercal tails. Extinct.
4. Class Chondrichthyes- Sharks, rays and chimera. 800 sp. Cartiligenous skeleton,
true jaws and fins, no operculum, internal fertilization, egg with yolk, auditory,
sight and olfactory organs. Sharks have regions in their skin that can pick up electric
fields generated by muscle contraction, as well as lateral lines. 5-7 external gill slits.
The largest is the whale shark, to 60' and 40 tons. 2 subclasses:
Holocephali: chimaeras (ratfish). No scales, one gill slit. Operculum present, bony
head fused to brain case, long skinny tail. Mollusk eaters. Have a clasping organ
Ratfish
on the head for mating.
Elasmobranchi: sharks and rays. Placoid scales, 5-7 gills. Sharks have paired fins, heterocercal tail, re
placement teeth.
5. Class Osteichthyes (bony fish): 30,000 species, which is almost 50% of all vertebrates. Most numerous of both species and individuals among vertebrates. They have a bony skeleton, true jaws
and fins, and an operculum. There are two subclasses:
1. Sarcopterygii (flesh-finned): represented today by two orders:
1. Dipnoi- Lungfishes: fish with lungs. 2 genera and 6 species extant, 4 in Africa, 1 in South
America and 1 in Australia.
2. Crossopterygii (lobe-finned): One ancient species extant, the coelacanth
(hollow spine), in the genus Latimeria. In bone structure and other ways
Crossopterygii resemble Amphibians and are thought to be their ancestors.
2. Actinopterygii (ray-finned): Most familiar fish; bases of fins are enclosed in
body wall, fins are supported by slender ray-like bones, scales extend under the
skin. Divided into 3 ‘superorders’:
1. Chondrostei: sturgeons and paddlefish. Largely cartiligenous skeleton and
Lungfish
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with a heterocercal tail (unequal upper and lower lobes).
2. Holostei: gar and bowfin. Skeleton well ossified, tail somewhat heterocercal.
3.Teleosti: ossified skeleton, tail usually homocercal (equal lobes).
6. Class Amphibia (double life): 4000 species, 6% of vertebrate life. All have gills at
some stage, lay eggs in water (or keep them moist), metamorphose, have moist permeable skin, and have a 3-chambered heart. All adults are carnivores. Most fertilize
externally. The oldest fossils are from the Devonian; they were the only vertebrates
on land in the Devonian and early Carboniferous. The largest known amphibian was
Eogyrinus (Greek, dawn tadpole), which grew alligator-like to 15' in the Devonian.
Chorus Frog
The largest today is the Chinese giant salamander at 3+ feet. 4 orders:
1. Caudata- Urodela (tailed): Salamanders. 390 species. Most are in the northern temperate zone. Internal
fertilization (via packets), well defined limbs, tails.
2. Anura (tailless): Frogs. 3843 species. Jumping adaptation (pelvic girdle fixed to vertebral column,
posterior vertebra fused into urostyle, radioulna), specialized tongue.
3. Apoda- Gymnophiona (legless ones): Burrowing amphibians. 165 species. World wide in the tropics. In
ternal fertilization, eggs or live birth, often blind, no trace of limb girdle, have scales (the only amphibians
that do).
4. Caecilians- Sirens: 6 families, 36 genera, 165 species.
7. Class Reptilia (Greek, ‘crawling’): 6000 species, 14% of vertebrate species. 8 characteristics: 1) exothermic, 2) 3-chambered heart and partial separation of blood flow, 3)
amniotic egg, 4) precotial young (miniature adult and no parental care), 5) lungs, 6)
epidermal scales, 7) complex lower jaw, 8) differentiation of vertebra into cervical,
lumbar, thoracic, sacral, caudal. Cotylosaurs ('stem lizards') were amphibian-like
creatures (now extinct) that laid an amniotic egg. There are 7 subclasses:
Garter Snake
1. Anapsida (Gr, no openings in the skull near the temples): 240 species, turtles.
very little changed since the Permian, which makes the one order, Chelonia, the most primitive living order. Characteristics include: amphibian limbs (permanent 'pushup'), 2) anapsid skull (no fenestra- gaps in
skull), 3) conspicuous bony covering dorsally and ventrally, the carapace and the plastron.
2. Ichthyopterygia: ichthoysaurs. Euryapids (a single hole in the temple region), dolphin-like. Extinct.
3. Synaptosauria: plesiosaurs. Euryapids, aquatic or semi-aquatic, long neck with thin body. Extinct.
4. Lepidosauria ('scaled reptiles'): Two orders:
1. Rhycocephalia ('snout-head'): single species, the Tautora (Mauri, 'black spine') or Sphenodon
('wedge-tooth') of New Zealand). Diapsid.
2. Squamata ('scaly'): Lizards and snakes. Modified diapsids. The largest is the Komodo Dragon, to
10'
and 365 lbs. Two suborders:
1. Lacertilia: Lizards. 3000 species.
2. Serpentes: Snakes. 3000 species. Ancestral snakes were apparently burrowing lizards. Have
chemical sensor tongue, keen eyes, no ears, left lung is reduced or absent.
5. Archosauria ('ruling reptiles'): 23 living species. The dinosaurs are/were included here. Diapsid (two
holes in the temple region of the skull). 1 living and 3 extinct orders:
1. Crocodilia: cross, alligators, caiman. Unchanged since the Mesozoic: 4chambered heart, advanced breathing system (diaphragm), well developed
voice.
2. Pterosauria: Flying reptiles. Enlarged 4th digit. Extinct.
3. Saurichia: Dinosaurs. Lizard-hipped, Quadra- and bi-pedal. Extinct.
4. Ornithisuchia: Dinosaurs. Bird-hipped, heavily armored, quadraped. Ex
tinct.
Caiman
6. Synapsida: mammal-like reptiles. Synapsids--one hole in the temple region of the skull.
7. Therapsid: Includes mammals and their ancestors.
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8. Class Aves: 8600 species. 22% of vertebrates. 23 orders. Evolved from dinosaurs
in Mesozoic. Characteristics: 1) feathers, 2) wings, 3) 4-chambered heart, 4) lungs, 5)
hollow bones, 6) no teeth, 7) modified jaw (beak), 8) homotherms, 9) large brains,
10) scaled feet, I I ) eggs (amniotic), 12) flight. Aves appeared in the Jurrassic.
They are evolved for flight, for example the skeleton of frigate birds have a wingspan of 6 feet and weighs 4 ounces. Adaptations for flight: 1) feathers, 2) pneumatic
Mountain Bluebird
bones, 3) thin skull, 4) toothless keritinized jaw, 5) crop and gizzard (can't chew
food), 6) fusion in skeleton (= fewer bones), in the repro system: 7) lays eggs (doesn't carry fetus), 8) seasonal
gonad changes, 9) female has only 1 ovary, 10) rapid and efficient digesting, 11) excrete uric acid (low moisture, small bladder). 12) high body body temp, 13) efficient respiratory system to fuel muscles and metabolism, 14) 4 chambered heart, 15) an energy-rich diet, 16) keel on the sternum for attachment of wing muscles..
If it weren't for the preservation of its feathers, Archeopteryx ('ancient wing', 140 million years ago) would
be regarded as another Archosauria. Many vertebrate zoologists argue that modern birds are living Archosaurs and should be classified as reptiles.
9. Class Mammalia: 4500 species, 10% of vertebrates, 20 orders. Arose from Therapsid reptiles which showed up in the late Permian; mammals first appear in the
Triassic. They coexisted with dinosaurs, and were about the size of a shrew, probably nocturnal (big eye sockets). Homeothermy may have evolved as an adaptation
to nocturnal life, pre-adapting mammals to the cooler climate of the late Cretaceous. Characteristics: 1) hair, 2) mammary glands, 3) homeothermy (constant
internal temp), 4) pelvic and pectoral girdles allow efficient locomation , 5) few
offspring with high parental investment 6) well developed brain.
Echidna
There are 1700 species of rodents, 875 of bats, 300 of shrews, 250 of carnivores, 190 of hoofed animals. Mammals are divided into 3 distinct subclasses:
1. Prototheria ('first beasts') or Monotremes ('one orifice'--the cloaca). Early divergence, perhaps Paleozoic. There are only 3 species extant, the platypus and 2 echidnas.
2. Metatheria ('middle beasts') or Marsupials ('pouched')- 240 species.
3. Eutheria ('true beasts') or placentals- 4000 species.
The Miocene was the golden age of mammals. The radiation of species peaked at that time; since then there
has been a decline in diversity and numbers. The appearance of humans outside of Africa at the end of the
Pleistocene had tremendous impact on fauna, with the extinction of much of the megafauna in North and
South America and in Australia.
Mammals are remarkably diverse, from tiny bats to whales. The bumblebee bat
from Thailand and Myanmar is 2-4 cm long and weighs 1.5 grams (there are 28
grams in 1 ounce). Some blue whales are more than 30 meters long and weigh as
much as 200 tons. This is the equivalent of three Brontosaurs. A blue whale heart
weighs 1/2 ton; a child could crawl through the major artery leaving it.
Marsupial-Sugar Glider
Kingdom Plantae
Plants began to colonize land about 450 million years ago. Several adaptations were required; gametes
had to disperse through a non-aquatic environment, and the plant and the embryo had to be protected from desiccation. Nearly all plants reproduce sexually, nearly all are capable of asexual reproduction. All employ alternation of generations, all are heteromorphic, with the diploid sporophyte more conspicuous in all but
bryophytes and allies. The 3 major stages of plant evolution are 1) the emergence onto land 450 million years
ago, requiring a cuticle and jacketed gametangia; 2) seeds, 360 million years ago, and 3) flowers (and attendant protected seeds), 140 million years ago. Plants are divided into 12 divisions, or phyla, as follows:
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1. Marchantiophyta- Liverworts, 9000 species. Liverworts have 3 basic growth
forms, foliose (leafy), fruitcose (stringy) and crustose (diminutive thallus attached
everywhere to substrate).
2. Anthocerotophyta- Hornworts, 100 species. Hornworts grow with green, flattened thallus; their name comes from the elongated, horn-like reproductive structure. They are found throughout the world but only in damp environments.
Liverwort
3. Bryophyta (Greek, ‘moss plant’)- 16,000 species. Mosses have 2 distinct adaptations for life on land, a cuticle
(a waxy covering on the leaves to prevent moisture loss) and gametes that develop in a gametangia, where they
are kept moist. The male gametangia is called the antherida, in which flagellated sperm are produced. They require water to swim to the female gametangia, the archegonium, where the egg releases a sugar that draws the
male by forced movement. Most bryophytes have no vascular transport; they must imbibe water like a
sponge. They are "elegantly adapted to a limited range of terrestrial habitats." They are not a precursor to
vascular plants. Their oldest fossils are 350 million years ago, by which time vascular plants already existed.
Spagnum mosses cover about 1% of the Earth’s terrestrial surface.
4. Lycophyta (Greek, ‘wolf plant’): About 1,000 sp in 5 genera. They were a major part
of the landscape in the Carboniferous, thriving for millions of years. One extinct line
had trunks 2 meters in die and heights to 50 meters (Lepidodendron; their bark is the
major constituent of carboniferous coal). The gametophytic generation is invisible underground for up to ten years, nurtured by symbiotic fungi. ‘Cannel coal' is derived
from the massive spore accumulations of ancient Lycophytes.
Clubmoss
5. Pteridophyta (Greek, ‘little feather plant’): Ferns and Horsetails, 12,000 species, 2/3 of which are in the tropics.
Flagellated sperm require moisture to swim to archegonia, dispersal is by spores. Spores give rise to a small, photosynthetic filament called a protonema, which grows into a small, heart-shaped, photosynthetic prothallus on
the ground. The sporophyte grows out of this.
The follow 4 divisions are Gymnosperms (Greek, ‘naked seed’): Gymnosperms were
the first to develop physiological strategies that allowed them to be free of the presence of liquid water for reproduction. In particular they replaced the flagellated
sperm with pollen transported by wind. They also retained the small gameotophytic
generation—the male stamens and female ovaries—within the large sporophyte generation, thus protecting them from desiccation, and they developed seeds for dispersal rather than spores.
Gingko
6. Ginkgophyta- One species exists today, Ginko biloba, is the only living descendant of a group that
was extensive in the Mesozoic. It is little changed from the mid-Paleozoic, where it appears among the
first fossil plants. Ginkgo is very resistant to pollution and insects.
7. Coniferophyta (‘cone plant’): About 600 species in 50 genera. Among the tallest
(redwoods up to 380'), largest (the General Sherman Sequoia is 80' in circumference) and oldest (bristlecone pines are over 5000 years) living things on
Earth. In Pinus fertilization occurs more than a year after pollination; cones usually
take 3 years to mature. The mature seed contains tissue from three plant generations
(the seed coat is from parent sporophyte, food reserves are from the female gametophyte, and embryo is the next sporophyte generation). The oldest conifer in the
fossil record dates from the Carboniferous, 300 million years ago. It is thought
that their drought-proof leaves evolved in the Permian, a time of world-wide aridity.
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BristleconePine
8. Gnetophyta (Latin gnetum is from Moluccan ganemu, a gnetophyte species found on the island of Ternate)70 species in 3 remotely related genera. Includes Ephedra trifurca, Mormon tea; there are 40 or so species of
Ephedra.
9. Cycadophyta- About 100 species in 9 genera, found only in tropical and subtropical regions. They are more closely related to angiosperms than to other gymnosperms. Primary roots can be as long as 36', secondary roots harbor cyanobacteria,
enabling cycads to populate nitrate-depleted areas.
Angiosperms- Anthophyta and angiosperm are two different names for the same
A Cycad
thing—flowering plants. The name angiosperm, which translates from the Greek as
‘little seed case, highlights one main difference between this group and the gymnosperms, which means
‘naked seed.’ Angiosperms have an additional layer of tissue surrounding the seed.
10. Anthophyta (Greek, ‘flower plant-)- 275,000 species in 300 families. There are at
least 4 evolutionary trends in flowers: 1) reduction in number of floral parts, 2) fusion of floral parts, 3) symmetry changed fin radial to bilateral, 4) The ovary shifted
fm superior to inferior position. Flowers are often designed specifically for pollination by one bird or insect. Many flowers produce ultraviolet 'nectar guides'
(invisible to humans) that lead pollinating insects to nectar, and thereby position
the creature for maximum pollination efficacy. Fruit often turns bright red and
sweet when ripe, which attracts birds and mammals (insects cannot see red well)
who are effective seed dispersers.
Saxifraga oppositifolia
“There is grandeur in this view of life, with its several powers, having been originally breathed into a few
forms or into one; and that, while this planet has gone cycling on according to the fixed law of gravity, from
so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”
Charles Darwin
“The main task of the immediate future is to assist in activating the inter-communion of all living and non-living beings in the emerging Ecozoic era of Earth development. What is most needed in order to accomplish
this task is the great art of intimacy and distance: the capacity of beings to be totally present to each other
while further affirming and enhancing the differences and identities of each.
Thomas Berry
“The value of science remains unsung by singers: you are reduced to hearing not a song or poem, but an evening lecture about it.“
Richard Feynman
“The statistical probability that organic structures and the most precisely harmonized reactions that typify living organisms would be generated by accident, is zero.“
Ilya Prigogine Recipient of two Nobel Prizes
“The human mind is not capable of grasping the Universe. We are like a little child entering a huge library. The
walls are covered to the ceilings with books in many different tongues. The child knows that someone must
have written these books. It does not know who or how. It does not understand the languages in which they
are written. But the child notes a definite plan in the arrangement of the books - a mysterious order which it
does not comprehend, but only dimly suspects.”
Albert Einstein
by Dana Visalli/[email protected]/www.methownaturalist.com,