Download Mammalian Characteristics

Biology 1407
Dr. Harold Kay
Chapter 28: The Origins of Eukaryotic Diversity
*Protista* Most primitive of eukaryotes and the first to evolve
 The Protista are the earliest descendants of prokaryotes.
 The are the simplest eukaryotes.
 Some are photoautotrophic while others are heterotrophic.
 When they are both photoautotrophic and heterotrophic we say they are
mixotrophic.
 Their habitats are mostly moist environments.
 They are very important in the food chain. Ex: Plankton
o Plankton: this is a community of organisms that are mostly microscopic
that swim passively and weakly near the surface of oceans, lakes and
pond. Important because they are the first line of our food chain.
 Unique Characteristics of Eukaryotes
o Membrane bound nucleus
o Have Mitochondria, Chloroplast, endomembrane system (rest of
organelles)
 Endomembrane system: contain nuclear envelope, ER,
Golgi apparatus, lysosome, vacuole
o They have a cytoskeleton.
o There flagella have the 9+2 microtubular structure.
o They have chromosomes that are composed of DNA and protein
molecules.
o They have a life style that includes mitosis, meiosis and sex
 Serial Endosymbiosis: The principle on serial endosymbiosis states that some
prokaryotes called endosymbionts are enclosed in larger prokaryotes.
 The traditional 5 kingdom classification was proposed by Robert Whittaker in
1969. MONERA, PROTISTA, PLANTAE, FUNGI AND ANIMALIA
 Protists are classified into 5 groups.
o These groups are called Candidate Kingdoms
 Candidate Kingdom Archeazoa
 They do not have Mitochondria
 Ex: Giardia lamblia: transmitted through water that is
contaminated with human feces. It cases diarrhea/
Dysentery. It is therefore a human parasite.
 Candidate Kingdom Euglenozoa
 They usually poses flagella
 They are also called the Flagellates.
 They are made up of 2 groups
o Euglenozoids
 Ex: Euglena: easy to grow on pools. Slime.
o Kinetoplastids
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

Trypanosome: the organism that causes
African sleeping sickness, which is
transmitted through they bite of the tse tse
fly.
 Candidate Kingdom Alveolata
 Made up of 3 main groups.
o Dinoflagellates: They usually have 2 flagella. They
do cause “red tide”, which is an explosive growth
called Bloom (looks like waves in oceans)
o Apicomplexans: These are also called the
sporozoans.
 Ex: Plasmodium/ causes Malaria. This is
transmitted through the bite of an Anopheles
Mosquito. They secrete a chemical that
deaden the skin. 4 o’clock disease
o Ciliates: They are also called the Ciliophorans.
They have numerous cilia
 Candidate Kingdom Straminopila
 These include organisms that contain different accessory
pigments, which include red, magenta and brown pigments.
These are use in the food industry as food coloring. Most
plant pathogens belong in this group.
 Candidate Kingdom Rhodophyta
 They do not have flagella. They are mostly used in the food
industry for there red color.
Alternation of Generation:
o This is the alternation of a multicellular haploid gamete produced by the
gametophyte and (alternation) and a multicelular diploid spore produced
by the sporophyte.
o The sporophyte is the familiar leafy plant that we know.
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Chapter 29: Plant Diversity: The colonization of Plants
o Some Plant Characteristics
 Cell walls
 Chloroplast: contain pigments called chlorophyll which are the sites of
photosynthesis.
 Plant food is starch. Starch is stored in plastids; ex: roots and tubers.
 Gas exchange in plants take place in special pores called stomata
 The surface of plants are coated with a waxy cuticle which protects plants
from drying out
 Plants have primary and secondary products
 Primary products are common to all plants.
 Ex: cellulose
 Secondary products arise from metabolic pathways.
 Ex: Lignin, which is what, makes plants to be woody.
*Plants as Embryophytes*
o When plants got on land they protected their gametes with an external covering
know as the Gametangia. As a result of this terrestrial adaptation plants became
known as EMBRYOPHTES.
*Highlights of Plant Phylogeny*
 There are 4 periods in plant evolution
o The origin of plants
 Plants originated about 475 million years ago.
 The produced jackets (Gametangia) to enclose their gametes
o Diversification of Seedless Plants
 Seedless vascular plants
 Plants without seed flourished during this period.
 Ex: ferns
o The Origin of Seeds
 Seeds originated about 360 million years ago.
 A seed is a plant embryo that contains food within a resistant coat.
 Some plants had seeds known as naked seeds.
 Plants that had naked seeds are called Gymnosperms.
 Ex: Conifers, Sego Palm, Cycad, Gingko
o Emergence of Flowering Plants
 These are the contemporary plants
 They are called the Angiosperms

o
 They also evolved vascular tissues to conduct and transport water, food and other
nutrients.
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*Classification of Plants*
 While it is Phylum in the Animal Kingdom it is called Division in the Plant
Kingdom
A. There are 11 divisions in the plant Kingdom with 4 groups of plants
1. Bryophytes: Non vascular plants (no tissue)
 3 Divisions
a. Bryophyta
b. Hepatophyta
c. Antothocerophyta
2. Pteridophytes: Are vascular plants that are seedless
 3 Division
a. Pteridophyta
b. Sphernophyta
c. Lycophyta
 .
3. Gymnosperms: These are vascular plants that have seeds
 4 Divisions
a. Coniferophyta
b. Cicadophyta
c. Gingkophyta
d. Gnetophyta
4. Angiosperm: These are the flowering plants. They are vascular
plants that have seeds and develop flowers.
 1 Division
a. Anthophyta
* Differentiation *
 When gametangia protect the male gamete it is called Antheridium.
 When gametangia protect the female gamete it is called Archigonium.
 Terrestrial adaptation of plants
A. Regional Specialization of plants
 Plants developed a root and shoot system
 Leaves were exposed to sunlight to make food.
B. Structural Support
 Plants developed trunks to stand upright.
 They also supported their stem by secreting lignin which makes
plants woody.
C. Vascular Tissue
 Vascular tissue developed for the conduction and transportation of
water, food and nutrients,
 2 types of vascular tissue
o Xylem: transports minerals from the roots to the
rest of the plant body.
o Phloem: conducts food throughout the plant body.
 When a plant grows on another plant using it as a substratum but are not parasites
they are called Epiphyte.
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
Some plants maybe male, female or both.
o Homosprous Sporophyte: will have a single spore. That single spore will
be a bisexual gametophyte. It will have the sperm and the egg.
o Heterosporous Sporophyte: will have a megaspore (female gametophyte/
egg) and a microspore (male gametophyte/sperm).
Chapter 30: Plant Diversity 2
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




In seed plants the seed replaced the spore as the main means of dispersal.
When additional tissues called integuments surround the seed it gives rise to the
fruit.
Different Parts of the Plant:
o Flower
o Carpel (the female part of the flower): stigma, style, ovary
o Stamen (the male part of the flower):
o Seed: a mature ovule. It consists of:
 Embryo
 Endosperm
 Seed coat
o
Coevolution: a reciprocal evolutionary response among 2 species which brings
about changes in response to evolutionary change in the other species. Ex: The
bright colors of fruits in response to animals desire for ripened fruit.
Relationship between Angiosperms and Agriculture:
o Agriculture is based almost entire on angiosperm
o There are about 260,000 plus species of plant. Out of this 2 dozen species
are used for food agriculture.
o Angiosperms provide nearly all of our food. Ex: fruits, agricultural crops
and grains (such as rice, fiber and wheat)
4 main uses of angiosperms:
o Medication
o Fibers
o Decoration
o Perfumes
*Global Impact of Plants*
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Chapter 31: Fungi
Overview

Ten thousand species of fungi have been described, but it is estimated that there
are actually up to 1.5 million species of fungi.
 Fungi play an important role in ecosystems, decomposing dead organisms, fallen
leaves, feces, and other organic materials.
This decomposition recycles vital chemical elements back to the environment in
forms other organisms can assimilate.
 Most plants depend on mutualistic fungi to help their roots absorb minerals and
water from the soil.
 Humans have cultivated fungi for centuries for food, to produce antibiotics and
other drugs, to make bread rise, and to ferment beer and wine.
Introduction to the Fungi
 Fungi are heterotrophs that acquire their nutrients by absorption.
They absorb small organic molecules from the surrounding medium.
Exoenzymes, powerful hydrolytic enzymes secreted by the fungus, break down food
outside its body into simpler compounds that the fungus can absorb and use.
The absorptive mode of nutrition is associated with the ecological roles of fungi as
decomposers (saprobes), parasites, and mutualistic symbionts.
Saprobic fungi absorb nutrients from nonliving organisms.
Parasitic fungi absorb nutrients from the cells of living hosts.
Some parasitic fungi, including some that infect humans and plants, are
pathogenic.
Fungi cause 80% of plant diseases.
Mutualistic fungi also absorb nutrients from a host organism, but they reciprocate
with functions that benefit their partner in some way.
Extensive surface area and rapid growth adapt fungi for absorptive nutrition.
 Yeasts are single-celled fungi. Most other species of fungi are multicellular.

The vegetative bodies of most fungi are constructed of tiny filaments called
hyphae that form an interwoven mat called a mycelium.
Fungal mycelia can be huge, but they usually escape notice because they are
subterranean.
 Fungal hyphae have cell walls.
These are built mainly of chitin, a strong but flexible nitrogen-containing
polysaccharide identical to that found in arthropods.
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
Most fungi are multicellular with hyphae divided into cells by cross walls, or
septa.
These generally have pores large enough for ribosomes, mitochondria, and even
nuclei to flow from cell to cell.
 Fungi that lack septa, coenocytic fungi, consist of a continuous cytoplasmic mass
with hundreds or thousands of nuclei.
This results from repeated nuclear division without cytoplasmic division.
 Parasitic fungi usually have some hyphae modified as haustoria, nutrientabsorbing hyphal tips that penetrate the tissues of their host.
 Some fungi even have hyphae adapted for preying on animals.
The filamentous structure of the mycelium provides an extensive surface area that suits
the absorptive nutrition of fungi.
One cubic centimeter of rich organic soil may contain 1 km of fungal hyphae with a
surface area of more than 300 cm2.
A fungal mycelium grows rapidly.
Proteins and other materials synthesized by the entire mycelium are channeled by
cytoplasmic streaming to the tips of the extending hyphae.
The fungus concentrates its energy and resources on adding hyphal length and absorptive
surface area.
 While fungal mycelia are nonmotile, by swiftly extending the tips of its hyphae it
can extend into new territory.
Fungi produce spores through sexual or asexual life cycles.

Fungi reproduce by producing vast numbers of spores, either sexually or
asexually.
The output of spores from one reproductive structure can be enormous.
Puffballs may release trillions of spores.
Dispersed widely by wind or water, spores germinate to produce mycelia if they land in a
moist place where there is food.
Many fungi have a heterokaryotic stage.
The nuclei of fungal hyphae and spores of most species are haploid, except for transient
diploid stages that form during sexual life cycles.

Sexual reproduction in fungi begins when hyphae from two genetically distinct
mycelia release sexual signaling molecules called pheromones.
Pheromones from each partner bind to receptors on the surface of the other.
 The union of the cytoplasm of the two parent mycelia is known as plasmogamy.
In many fungi, the haploid nuclei do not fuse right away.
 In some species, heterokaryotic mycelia become mosaics, with different nuclei
remaining in separate parts of the same mycelium or mingling and even
exchanging chromosomes and genes.
 In some fungi, the haploid nuclei pair off two to a cell, one from each parent.
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Such a mycelium is called dikaryotic, meaning “two nuclei.”

In many fungi with sexual life cycles, karyogamy, fusion of haploid nuclei
contributed by two parents, occurs well after plasmogamy, cytoplasmic fusion of
cells from the two parents.
The delay may be hours, days, or even centuries.
During karyogamy, the haploid nuclei contributed by the two parents fuse, producing
diploid cells.
In most fungi, the zygotes of transient structures formed by karyogamy are the only
diploid stage in the life cycle.
These undergo meiosis to produce haploid cells that develop as spores in specialized
reproductive structures.
These spores disperse to form new haploid mycelia.
The sexual processes of karyogamy and meiosis generate genetic variation.
The heterokaryotic condition also offers some of the advantages of diploidy, in that one
haploid genome may be able to compensate for harmful mutations in the other.
Many fungi reproduce asexually.
The processes of asexual reproduction in fungi vary widely.
Some species reproduce only asexually.
Some fungi that can reproduce asexually grow as mold.
Molds grow rapidly as mycelia and produce spores.
Yeasts live in liquid or moist habitats.
Instead of producing spores, yeasts reproduce asexually by simple cell division or by
budding of small cells.
Most molds and yeasts have no known sexual stage.
Such fungi are called deuteromycetes, or imperfect fungi.
Whenever a sexual stage of a deuteromycete is discovered, the species is classified in
a particular phylum depending on its sexual structures.
Fungi can be identified from their sexual stages and by new genetic techniques.
Diversity of Fungi
Data from paleontology and molecular systematics offer insights into the early evolution
of fungi.
Systematists recognize Fungi and Animalia as sister kingdoms.
Fungi and animals are more closely related to each other than they are to plants or
other eukaryotes.
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Phylum Chytridiomycota: Chytrids may provide clues about fungal origins.
Phylogenetic systematics suggests that fungi evolved from a unicellular, flagellated
protist.
The lineages of fungi that diverged earliest (the chytrids) have flagella.
Members of the clade Opisthokonta, including animals, fungi, and closely related
protists, possess flagella.
This name refers to the posterior (opistho) location of the flagellum.
Scientists estimate that the ancestors of animals and fungi diverged into separate lineages
1.5 billion years ago.
However, the oldest undisputed fungal structures are only 460 million years old.
It is likely that the first fungi were unicellular and did not fossilize.
Fungi underwent an adaptive radiation when life began to colonize land.
Fossils of the first vascular plants from the Silurian period contain evidence of
mycorrhizae, symbiotic relationships between plants and subterranean fungi.
Fungi have radiated into a diverse set of lineages.
Fungi classified in the phylum Chytridiomycota, called the chytrids, are ubiquitous in
lakes, ponds, and soil.
Some are saprobes, while others parasitize protists, plants, and animals.
However, recent molecular evidence supports the hypothesis that chytrids diverged
earliest in fungal evolution.
Like other fungi, chytrids use an absorptive mode of nutrition, have chitinous cell walls,
and have similar key enzymes and metabolic pathways.
While there are a few unicellular chytrids, most form coenocytic hyphae.
Chytrids are unique among fungi in having flagellated spores, called zoospores.
Until recently, systematists thought that fungi lost flagella only once in their history, after
chytrids had diverged from other lineages.
However, molecular data now indicates that some flagellated fungi are more closely
related to another fungal group, the zygomycetes.
If this is true, flagella were lost on more than one occasion during fungal evolution.
Phylum Zygomycota: Zygote fungi form resistant structures during sexual
reproduction.
The 1,000 zygomycetes exhibit a considerable diversity of life history.
The phylum includes fast-growing molds, parasites, and commensal symbionts.
The life cycle and biology of Rhizopus stolonifer, black bread mold, is typical of
zygomycetes.
The hyphae are coenocytic, with septa found only where reproductive cells are formed.
Horizontal hyphae spread out over food, penetrate it, and digest nutrients.
In the asexual phase, hundreds of haploid spores develop in sporangia at the tips of
upright hyphae.
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Some zygomycetes, such as Pilobolus, can actually aim their sporangia toward
conditions that would be favorable for their spores.
If environmental conditions deteriorate, Rhizopus may reproduce sexually.
Plasmogamy of opposite mating types produces a zygosporangium.
Inside this multinucleate structure, the heterokaryotic nuclei fuse to form diploid
nuclei that undergo meiosis.
The zygosporangia are resistant to freezing and drying.
When conditions improve, the zygosporangia undergo meiosis and release haploid spores
that colonize new substrates.
Microsporidia are unicellular parasites.
Microsporidia are unicellular parasites of animals and protists.
They are often used in biological control of insect pests.
Microsporidia lack conventional mitochondria, and represent something of a taxonomic
mystery.
Some researchers suggest that they are an ancient, deep-branching eukaryotic lineage.
Recent evidence suggests that they are highly derived parasites that may be related to
zygomycete fungi.
Glomeromycetes form mycorrhizae.
Only 160 species of glomeromycetes have been identified.
Nonetheless, they are an economically significant group.
All glomeromycetes form symbiotic mycorrhizae with plant roots.
Mycorrhizal fungi can deliver phosphate ions and other minerals to plants.
In exchange, the plants supply the fungi with organic nutrients.
There are several different types of mycorrhizal fungi.
Ectomycorrhizal fungi form sheaths of hyphae over the surface of the plant root and
grow into the extracellular spaces of the root cortex.
Endomycorrhizal fungi extend their hyphae through the root cell wall and into tubes
formed by invagination of the root cell membrane.
Glomeromycetes all form a distinct type of endomycorrhizae called arbuscular
mycorrhizae.
The tips of the hyphae that push into plant root cells branch into tiny treelike
structures known as arbuscles.
Such symbiotic partnerships with glomeromycetes are present in 90% of all plants.
Phylum Ascomycota: Sac fungi produce sexual spores in saclike asci.
Mycologists have described more than 32,000 species of ascomycetes, or sac fungi, from
a variety of marine, freshwater, and terrestrial habitats.
Ascomycetes produce sexual spores in saclike asci and are called sac fungi.
Most ascomycetes bear their sexual stages in fruiting bodies called ascocarps.
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They range in size and complexity from unicellular yeasts to elaborate cup fungi and
morels.
Some are devastating plant pathogens.
Many are important saprobes, particularly of plant material.
About 40% of ascomycete species live with green algae or cyanobacteria in mutualistic
associations called lichens.
Some ascomycetes form mycorrhizae with plants or live between mesophyll cells in
leaves where they may help protect the plant tissue from insects by releasing
toxins.
Ascomycetes reproduce asexually by producing enormous numbers of asexual spores,
which are usually dispersed by the wind.
These naked spores, or conidia, develop in long chains or clusters at the tips of
specialized hyphae called conidiophores.
Ascomycetes are characterized by an extensive heterokaryotic stage during the formation
of ascocarps.
Plasmogamy between two parental hyphae produces a heterokaryotic bulge called an
ascogonium.
The coenocytic ascogonium extends hyphae that are partitioned by septa into dikaryotic
cells, each with two haploid nuclei representing two parents.
The cells at the tip of these dikaryotic hyphae develop into asci.
Within an ascus, karyogamy combines the two parental genomes, and meiosis forms four
genetically different nuclei forming eight ascospores.
In many asci, the eight ascospores are lined up in a row in the order in which they
formed from a single zygote nucleus.
One of the best-studied ascomycetes is Neurospora crassa, a bread mold.
This ascomycete serves as a model organism.
In 2003, its entire genome was published.
With 10,000 genes, the genome of this tiny fungus is three-fourths the size of the
Drosophila genome and one-third the size of the human genome.
The Neurospora genome is compact, with few stretches of noncoding DNA.
Neurospora may have a genomic defense system to prevent “junk DNA” from
accumulating in its genome.
Phylum Basidiomycota: Club fungi have long-lived dikaryotic mycelia.
Approximately 30,000 fungi, including mushrooms and shelf fungi, are called
basidiomycetes and are classified in the phylum Basidiomycota.
The name of the phylum is derived from the basidium, a transient diploid stage.
The clublike shape of the basidium is responsible for the common name club fungus.
Basidiomycetes are important decomposers of wood and other plant materials.
Of all fungi, the saprobic basidiomycetes are best at decomposing the complex
polymer lignin, abundant in wood.
The life cycle of a club fungus usually includes a long-lived dikaryotic mycelium.
Environmental cues, such as rain or temperature change, induce the dikaryotic mycelium
to reproduce sexually by producing elaborate fruiting bodies called basidiocarps.
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A mushroom is a familiar basidiocarp that can pop up overnight as it absorbs water
and as cytoplasm steams in from the dikaryotic mycelium.
The dikaryotic mycelia are long-lived, generally producing a new crop of
basidiocarps each year.
The cap of a mushroom supports and protects a large surface area of basidia on the gills.
The basidia form sexual spores called basidiospores.
A common white mushroom has a gill surface of about 200 cm2 and may release a
billion basidiospores, which drop from the cap and blow away.
Asexual reproduction is much less common in basidiomycetes than in ascomycetes.
Ecological Impacts of Fungi
Ecosystems depend on fungi as decomposers and symbionts.
Fungi are important decomposers of organic material, including cellulose and lignin of
plant cell walls.
Fungi and bacteria are essential for providing ecosystems with the inorganic nutrients
responsible for plant growth.
Without decomposers, carbon, nitrogen, and other elements would become tied up in
organic matter.
Fungi form symbiotic relationships with plants, algae, and animals.
Mycorrhizae are extremely important in natural ecosystems and agriculture.
Almost all vascular plants have mycorrhizae and rely on their fungal partners for
essential nutrients.
Some fungi break down plant material in the guts of cows and other grazers.
Many species of ants and termites raise fungi in “farms” and feed them leaves.
The fungi break the leaves down into a substance that the insects can digest.
Some mutualistic associations between “farmer” insects and “farmed” fungi have
been established for more than 50 million years.
In many cases, the fungi can no longer survive without the insects.
Lichens are a symbiotic association of millions of photosynthetic microorganisms held in
a mesh of fungal hyphae.
The fungal component is commonly an ascomycete, but several basidiomycete lichens
are known.
The photosynthetic partners are usually unicellular or filamentous green algae or
cyanobacteria.
The fungal hyphae provide most of the lichen’s mass and give it an overall shape and
structure.
The algae or cyanobacteria usually occupy an inner layer below the lichen surface.
The merger of fungus and algae is so complete that they are actually given genus and
species names, as though they were single organisms.
More than 13,500 species of lichen have been described—a fifth of all known fungi.
In most lichens, each partner provides things the other could not obtain on its own.
For example, the alga provides the fungus with food by “leaking” carbohydrate from
their cells.
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The cyanobacteria provide organic nitrogen through nitrogen fixation.
The fungus provides a suitable physical environment for growth, retaining water and
minerals, allowing for gas exchange, shading the algae or cyanobacteria from
intense sunlight with pigments, and deterring consumers with toxic compounds.
The fungus also secretes acids, which aids in the uptake of minerals.
The fungi of many lichens reproduce sexually by forming ascocarps or basidiocarps.
Lichen algae reproduce independently by asexual cell division.
Asexual reproduction of symbiotic units occurs either by fragmentation of the parental
lichen or by the formation of structures called soredia, small clusters of hyphae with
embedded algae.
Phylogenetic studies of lichen DNA have helped illuminate the evolution of this
symbiosis.
Molecular studies published in 2001 support the hypothesis that all living lichens can be
traced to three original associations involving a fungus and a photosynthetic
symbiont.
The same studies also suggest that many free-living fungi, including Penicillium,
descended from lichen-forming ancestors.
Lichens are important pioneers on newly cleared rock and soil surfaces, such as burned
forests and volcanic flows.
The lichen acids penetrate the outer crystals of rocks and help break down the rock.
This allows soil-trapping lichens to establish and starts the process of succession.
Nitrogen-fixing lichens also add organic nitrogen to some ecosystems.
Some lichens can survive severe cold or desiccation.
In the arctic tundra, herds of caribou and reindeer graze on carpets of reindeer lichens
under the snow in winter.
In dry habitats, lichens may absorb water quickly from fog or rain, gaining more than
ten times their mass in water.
Lichens are particularly sensitive to air pollution, and their deaths can serve as an early
warning of deteriorating air quality.
Some fungi are pathogens.
About 30% of the 100,000 known species of fungi are parasites, mostly on or in plants.
Invasive ascomycetes have had drastic effects on forest trees such as American elms
and American chestnuts in the northeastern United States.
Other fungi, such as rusts and ergots, infect grain crops, causing tremendous
economic losses each year.
Fungi are also serious agricultural pests.
Between 10% and 50% of the world’s fruit harvest is lost each year to fungal attack.
Some fungi that attack food crops produce compounds that are harmful to humans.
For example, the mold Aspergillus can contaminate improperly stored grains and
peanuts with aflatoxins, which are carcinogenic.
Poisons produced by ergots of the ascomycete Claviceps purpurea can cause
gangrene, nervous spasms, burning sensations, hallucinations, and temporary
insanity when infected rye is milled into flour and consumed.
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One of the compounds to have been isolated from ergots is lysergic acid, the raw
material from which the hallucinogen LSD is made.
Animals are much less susceptible to parasitic fungi than are plants.
Only about 50 fungal species are known to parasitize humans and other animals, but
their damage can be disproportionate to their taxonomic diversity.
The general term for a fungal infection is mycosis.
Infections of ascomycetes produce the disease ringworm, known as athlete’s foot
when they grow on the feet.
Systemic mycoses spread through the body and cause very serious illnesses.
They are typically caused by inhaled spores.
Coccidiodomycosis is a systemic mycosis that produces tuberculosis-like symptoms
in the lungs.
It is so deadly that it is now considered a potential biological weapon.
Some mycoses are opportunistic, occurring only when a change in the body’s
microbiology, chemistry, or immunology allows the fungi to grow unchecked.
Candida albicans is a normal inhabitant of moist epithelia such as human vaginal
lining, but it can become an opportunistic pathogen.
Other opportunistic mycoses have become more common due to AIDS, which
weakens the immune system.
Fungi are commercially important.
In addition to the benefits that we receive from fungi in their roles as decomposers and
recyclers of organic matter, we use fungi in a number of ways.
Most people have eaten mushrooms, the fruiting bodies (basidiocarps) of
subterranean fungi.
The fruiting bodies of certain mycorrhizal ascomycetes, truffles, are prized by
gourmets for their complex flavors.
The distinctive flavors of certain cheeses come from the fungi used to ripen them.
The ascomycete mold Aspergillus is used to produce citric acid for colas.
Yeasts are even more important in food production.
Yeasts are used in baking, brewing, and winemaking.
The yeast Saccharomyces cerevisiae is the most important of all cultured fungi, and is
available in many strains as baker’s and brewer’s yeast.
Contributing to medicine, some fungi produce antibiotics used to treat bacterial diseases.
In fact, the first antibiotic discovered was penicillin, made by the common mold
Penicillium.
A compound extracted from ergots is used to reduce high blood pressure and stop
maternal bleeding after childbirth.
Fungi play an important role in molecular biology and biotechnology.
Researchers use Saccharomyces to study the molecular genetics of eukaryotes.
Scientists have learned about the genes involved in Parkinson’s and Huntington’s
diseases by examining the homologous genes in Saccharomyces.
Genetically modified fungi are used to produce human glycoproteins.
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CHAPTER 32 SUMMARY-ANIMAL EVOLUTION
CHARACTERISTICS OF ANIMALS
1. They are multicellular and eukaryotic organisms.
2. Heterotrophy is by ingestion. Ingestion is eating other organisms or decomposing
organic matter. Carbohydrate reserves are stored as glycogen.
3. Cell walls are absent. They have intercellular junctions e.g, desmosomes, gap
junctions and tight junctions.
4. Their body cells are highly differentiated and organized into tissues, organs and
organ systems for digestion, reproduction, respiration and transport.
5. Nervous tissue for impulse conduction and muscle tissue for movement.
6. Reproduction is typically sexual and results in a zygote which undergoes mitotic
division known as cleavage which produces a blastula and then a gastrula.
Cleavage
Is a succession of mitotic cell divisions without cell growth between the division cycles,
that converts the zygote into a ball of cells.
Blastulation (Blastula)
Is a multicellular stage that takes the form of a hollow ball of cells that mark the end of
cleavage during embryonic development.
Gastrulation (Gastrula)
Two layered embryonic tissues that develop into adult body parts called the gastrula.
When animals are classified using tissue as the criterion the following groupings arise:
Using tissue:
Parazoans (lack true tissues)
Animals
Eumetazoans (true tissues)
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Using body symmetry:
Oral (top)
2 germ
layers
Radiata- radial symmetry
Aboral (bottom)
Eumetazoans
-Have no front, no back, no right or left
Bilateria- Bilateral
symmetry
Dorsal (top)
Ventral (bottom)
Anterior- (head)
Posterior- (tail)
3 germ
layers
– Have cephalization (centralization of
sensory structures in the head area)
2 germ layers
Ectoderm
Endoderm
3 germ layers
Ectoderm
Mesoderm
Endoderm
Diploblastic e.g.
cnidarians,
ctenophora
Triploblastic
Using body cavity:
Triploblastic
Acoelomate (no body cavity) e.g. platyhelminthes
Pseudocoelomate (fluid-filled) e.g. nematoda
Coelomate (fluid-filled & lined with tissues) e.g. annelida
Notes:
Acoelomate- an animal body plan characterized by no body cavity present between the
digestive tract and the outer body wall.
Pseudocoelomate- animal body plan characterized by a fluid filled body cavity that
separates the digestive tract and the outer body wall.
Coelomate- animal body plan characterized by a fluid filled body cavity completely lined
with tissue derived from the mesoderm.
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Based on differences in development. These developmental differences include:
1. Cleavage pattern
2. Coelom formation
3. Fate of blastopore
Spiral
Protostomes
Cleavage:
Coelomate
Determinat
e
Coelom: Schizocoelous
Deuterostome
E.g.
mollusks,
annelids,
arthropods
Blastopore: blastopore forms mouth
Cleavage:
Radial
Indeterminate
E.g.
echinoderms,
chordates
Coelom: Enterocoelous
Blastopore: blastopore forms anus
Note:
Blastopore is the first opening of the archenteron, which forms during gastrulation.
In protostomes the blastopore forms the mouth.
In deuterostome the blastopore forms the anus.
Archenteron is a primitive gut.
Spiral cleavage- cleavage in which the planes of cell division are diagonal to the
diagonal axis of the embryo.
Determinate cleavage- cleavage in which the developmental fate of which embryonic
cell is established very early
Radial cleavage- cleavage during which the cleavage planes are either parallel or
perpendicular to the vertical axis of the embryo.
Indeterminate cleavage- cleavage in which each early embryonic cell retains the
capacity to develop into a complete embryo if isolated from other cells.
Enterocoelous- Coelom development fount in deuterostomes where the coelomic
cavities form mesoderm buds from the wall of the Archenteron buds out.
Schizocoelous- Coelomic development found in protostomes where solid masses of
mesoderm split to form coelomic cavities.
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Protostomes
Spiral cleavage
Determinate cleavage
Blastopore forms the mouth
Schizocoelous Coelom formation
Deuterostome
Radial cleavage
Indeterminate cleavage
Blastopore forms the anus
Enterocoelous Coelom formation
Chapter 33: Invertebrates
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Organisms without a back bone
There are about 1 million species of animals today. 95% are invertebrates.
Most invertebrates don’t have tissues; as a result they are mostly Parazoans.
Ex: Sponge: an organism at the bed of oceans usually situated on a bed of rocks.
They do not have nerves or muscles.
They are suspension feeders:
They have only one opening and as a result have a gastrovascular cavity.
They are mostly Hermaphroditic:
Humans get infected with tapeworm by eating undercooked beef or pork.
Parthenogenesis: The production of offspring by a female from an unfertilized
egg.
Entomology: the study of insects:
Most insects undergo metamorphosis.
Metamorphosis is the development of an organism from the egg to the adult stage.
2 types of metamorphosis:
o Incomplete Metamorphosis: This is the development during which the
young resembles the adult except that they are smaller and have different
body proportions. The stages are from Egg to Pupa/Cocoon (resting stage)
from this the adult develops.
o Complete Metamorphosis: This is the development that is characterized by
the egg which produces the larva/caterpillar/maggot/grub (Eating Stage)
which results in the Pupa/ cocoon (resting stage) which produces the adult.
These stages are different in appearance and proportion to the adult.
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CHAPTER 34-SUMMARY-VERTEBRATE EVOLUTION AND DIVERSITY
The phylum Chordata includes three subphyla: two invertebrate subphyla- Urochordata
and Cephalochordate & a vertebrate subphyla- Vertebrata.
CHARACTERISTICS OF PHYLUM CHORDATA
Chordates are Deuterostomes. They have FOUR characteristics, which appear at some
time during the animal’s life. They are:
1. Notochord
Is a longitudinal flexible rod located between the gut and the nerve cord? It extends
through most of the length of the animal as a simple skeleton. In most vertebrates it is
a more complex jointed skeleton that develops. The notochord is retained in adults as
the material of the disc between the vertebrae.
2. Dorsal, hollow nerve cord
The brain and spinal cord, which make up the central nervous system, develop from
this nerve cord.
3. Pharyngeal slits
Chordates have a complete digestive system (mouth and anus). The pharynx is the
region posterior to the mouth and it opens to the outside through several pairs of slits.
They have become modified for gas exchange and other functions during the
evolution of vertebrates.
4. Muscular postanal tail.
A tail extending beyond the anus. Provides much of the propulsive force in many
aquatic species.
Notes:
Paedogenesis- precocious attainment of sexual maturity in a lava.
Synapomorphies- this is when vertebrates retain primitive chordate features while
adding other specializations.
Phylum ChordataMade up of 3 subphyla.
Two are invertebrates.
The other is vertebrate.
Urochordat
a
Invertebrates
Cephalochordata
Vertebrata
Vertebrate
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The vertebrates are divided into 2 major groups or superclasses, namely: Agnatha &
Gnathastomata
Superclass Agnatha (lack Jaws)
Vertebrate
Superclass Gnathastomata (have Jaws)
Chondrichthyes- Cartilage
Gnathastomata
Ostichthyes- Bony
Pisces
Amphibians
Reptiles
Tetrapods
Aves
Mammals
Tetrapod- are animals that possess two pairs of limbs that support them on land.
Reptiles, Aves and mammals have features of the amniotic condition and are therefore
called AMNIOTES.
Ratites (flightless)
Aves
Carinates (flight)
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Mammalian Characteristics
1. Hair, which is composed, of keratin provides insulation.
2. Active metabolism. Are endotherms. Four chambered heart
3. Mammary glands that produce milk to nourish the young.
4. Teeth with different sizes and shapes for chewing many types of foods.
5. Mammals are dioecious with sexual reproduction and internal fertilization. Most
are viviparous. A few are oviparous.
Notes:
Viviparous- the young develops within the uterus, nourished from the mothers blood
through the placenta e.g. humans
Oviparous- lay eggs that hatch outside the mother’s body
Ovoviviparous- retains fertilized egg in oviduct. Nourished by egg yolk, embryo
develops into young, born after hatching.
MARSUPIALS
This group includes, opossums, kangaroos, koalas and other mammals that complete their
development in a marsupium (maternal pouch)
MODERN PRIMATES
They are divided into two suborders namely:
1. Prosimii (premonkeys)
2. Andropoidea (monkeys, apes, and humans)
Paleoanthropology- the study of human origin and evolution.
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THE FIRST HUMANS
Australopithecus africanus- was discovered by Raymond dart in 1924.
“Lucy” an Australopithecus skeleton was discovered in 1974 in Ethiopia, Africa by
Paeleanthropologists.
Lucy is 3.2 million years old.
Since 1994 other hominids have been discovered in east Africa. They include:
Australopithecus anamensis
Australopithecus ramidus.
Australopithecus afarensis
The emergence of the human brain was first evident in fossils about 205 million years
ago.
As a result of this, paleoanthropologists believe these advances warrant placing these
organisms in the genus “homo”. Homo habilis etc.
Homo erectus and it’s descendants
Homo erectus was the first hominid to migrate OUT OF AFRICA. Homo erectus was
taller and had a larger brain than h. habilis.
Homo erectus lived in huts or caves, built fires, wore clothes of skins and designed better
stone tools.
Origin of modern humans.
While the debate still continues, there are two known models of the origin of modern
humans.
1. The multiregional model- modern humans evolved along the same lines in
different parts of the world. The Neanderthals and post homo erectus hominids
were ancestors to modern humans. It is assumed that interbreeding among
neighboring populations provided opportunities for gene flow over the entire
range and resulted in the genetic similarity of modern humans.
African
n
European
ANan
East Asian
asianAsian
asian
Australasia
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2. The monogenesis model- modern humans dispersed from Africa. Homo
erectus was the ancestor to modern humans who evolved in Africa. The diversity of
modern humans has developed from geographical diversity. That is, an exclusively
African genesis for modern humans is strongly indicated by the fact that the complete
transition from archaic Homo sapiens to modern humans is found only in African
fossils.
African
European
East Asia
Australasia
Chapter 38:
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Some flower maybe complete or incomplete.
o Complete Flower: one that has a sepal, petal, stamen, and Carpel
o Incomplete Flower: one that lacks one of the above parts.
Perfect Flower: one that is both Staminate (male) and Carpilate (female)
Imperfect Flower: one that lacks a stamen or a carpel/ either Staminate or
Carpilate. They are usually called Uni-sex Flowers.
Monecious: a plant that has both stamen and carpel on the same individual plant.
Dioecious: a plant that has the stamen or the carpel on separate plants.
Monoculture: This is the cultivation of large areas of land with the same plant
species.
Disadvantages of Monoculture:
o Weather
o Depletion of soil nutrients
o Disease
S-Gene (s stands for self-incompatibility/ the rejection of a pollen grain from the
same or closely related plant by its stigma) the gene responsible for this rejection
is called the s-gene.
Most agricultural plants are self compatible, which is why farmers practice
monoculture.
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Seeds go from Seeds to Seedling
There are 4 stages to produce a seedling from a seed
o Imbibition: when seeds absorption of water and consequent swelling of
seeds.
o Storage: The Storage of Materials/ Nutrients by the seeds which are then
digested by enzymes.
o The Emergence of the Radical: radical (embryonic root) emergences from
the seed.
o The Shoot tip breaks the soil/ ground level and emerges. It is also called
the cotyledon.
Asexual reproduction in plants is also called Vegetative reproductive.
There are 2 mechanisms of vegetative Reproduction
o Fragmentation: when the plant breaks into several pieces.
o Apomixis: when plants produce seeds without fertilization.
 E: Dandelions:
Cellular Mechanisms of Plant Development
 The changes from a fertilized egg to a plant involve- growth, morphogenesis
and cellular differentiation.
 Growth is an irreversible increase in size resulting from cell division and cell
enlargement.
o The zygote divides mitotically to produce a multicellular embryo in the
seed.
o Mitosis resumes in the root and shoot apical meristems after germination.
o Enlargement of the newly produced cells results in most of the actual size
increase.
 Morphogenesis is the development of body shape and organization.
o Begins in the early divisions of the embryo to produce the cotyledons and
rudimentary roots and shoots.
o Continues to shape the root and shoot system as the plant grows
o The meristems which remain embryonic continue growth and
morphogenesis throughout the life of the plant.
 Cellular differentiation is the divergence in structure and function of cells as
they become specialized during the plants development.
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Plant cells are organized into tissues and organs at specific locations based on
embryonic instructions.
o Pattern Formation: this is the development of specific structures in
specific locations on the plant. This is informed by signals that indicate the
locations of different parts of the plant relative to other cells. This is called
positional information. Positional information therefore tells pattern
formation what to do.
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