Download Evolution and Diversity of Life

Evolution and Diversity
of Life
Module 4 Topics:
Chapter 14: Origin of Life
Chapter 15: Evidence and Theory
Chapter 16: Populations & Species
Chapter 17: Human Evolution
Chapter 18: Classification
Chapter 14: Origins of Life
• Biogenesis: “All living things (currently) come
from other living things”
– This seems reasonable, but has not always been
accepted. At one time, spontaneous generation
myths were widespread.
• Spontaneous generation: The largely
discredited belief that living things could easily
arise from non living things.
– These are now mostly considered myths, but it can be
argued that spontaneous generation must have taken
place at least once
Spontaneous Generation Myths
•
•
•
•
Can maggots be created from rotten meat?
Can rice grains turn into mice?
Can mud turn into fish?
Can broth turn into germs?
–At one time people believed all of the
above ideas. Today we know that these are
just myths.
–No careful observer has ever observed rice turning
into mice. We now know maggots are actually baby
flies, whose eggs were laid in the rotten meat.
Spontaneous Generation was
Disproved by Experimentation
• Francisco REDI’s Experiment
– Proved maggots come from fly eggs. P.261
• Lazzaro SPALLANZANI’s Experiment
– Showed micro-organisms do not grow in
sealed jars (but excluded oxygen) P. 262
• Louis PASTEUR’s Experiment
– Proved micro-organisms are carried in dirty
air, not spontaneously generated (his
experiment allowed clean air in) P. 263
Abiogenesis:
Spontaneous Generation Once Long Ago
• So how did life get here if spontaneous
generation does not take place?
• It must have happened once-upon-a-time!
• Remember: The world 4 billion years ago
was very different from what it is now.
– Atmosphere then: Hydrogen (H2), Methane
(CH4), Ammonia(NH3), Carbon dioxide(CO2),
Water vapour
– Atmosphere now: Nitrogen (≈78%), Oxygen
(≈21%), Carbon dioxide (<1%), Water vapour
(variable), Argon (trace)
Age of the Earth:
•
•
•
•
•
•
•
•
•
Big Bang:
Sun formed
Earth formed:
Earth cooled:
First Life formed:
Multicellular life:
Reptiles
End of dinosaurs
Hominids
≈13.7 billion years ago
=5 or 6 billion years ago
≈ 4.5 billion years ago
≈ 4.0 billion years ago
c. 3.2 to 3.8 billion years ago
≈ 500 million years ago
≈ 250 million years ago
≈ 65 million years ago
> 3 million years ago
Geological Clock
Ancient Earth
• The world 4 billion years ago was very
different from what it is now.
– The atmosphere had more Hydrogen (H2),
Methane (CH4), Ammonia(NH3), and Carbon
dioxide(CO2) than it does now
– The earth was warmer, with seas just below
boiling
– The weather more violent, with powerful
thunderstorms
Oparin’s Hypothesis
• In 1923 Alexander Oparin
suggested that the conditions on
early earth could give rise to organic
compounds spontaneously.
• To demonstrate Oparin’s
hypothesis in 1953 two graduate
students (Harold Urey & Stanley
Miller ) built an apparatus containing
the gases he believed were present
in the early atmosphere
Alexander Oparin
Harold C.
Urey
Stanley
Miller
Miller & Urey’s Device
• They filled the bottom of their
device with water, and heated it
to simulate warm ancient oceans
• They used a spark chamber to
simulate lightning
• After running this device for
several weeks they discovered
that they had produced several
organic compounds, including
amino acids
Enlarged diagram of Urey-Miller apparatus
“Primordial Soup”
• The main hypothesis coming from Miller and
Urey’s experiment and Oparin’s original
hypothesis is that the early Earth’s oceans filled
with organic compounds, becoming a sort of
primordial ooze, slime or soup.
• Within this more concentrated organic soup, it
was possible for the right arrangement of
chemicals to come together to form a primitive
form of life.
Alternate Theories
• Some Biologists have suggested other mechanisms for
making complex compounds, and variations on Oparin’s
“Primordial Soup” hypothesis, including:
• The organic compounds may have become even more
concentrated in shallow pools along the ocean shore
• Organic compounds could have come together in pores in
rocky or sandy surfaces.
• Life may have started in deep ocean hydrothermal vents.
• Some organic compounds may have formed in space or on
other planets, and been brought to Earth on meteorites.
“There are those who believe life here began out
there, far across the universe.”
(I recall an old SF show that started with those exact words.)
Chapter 15: Theory and Evidence
• In this chapter we will examine the
evidence that life has changed over time.
• We will look at several theories about how
those changes have occurred.
Fossils
A fossil is a trace of a long-dead
organism
There are many types of fossils
• Mold fossils are imprints, like
footprints, and impressions of skin,
feathers or bark
• Cast fossils are made when the
remains of ancient things are filled
with minerals, like fossilized bones
or petrified wood.
• Fossils can also be preserved in
amber (fossilized plant resin) or tar
(a thick form of crude oil)
Who discovered fossils?
• Fossils have been dug up for centuries. In
ancient China some fossils were called
“dragon bones”
• The first European to realize that fossils
were the remains of extinct animals was
Robert Hooke (the same guy who first
observed dead cells)
Layers of Fossils
• In general, fossils exist buried in
sedimentary rock layers laid
down on the bottom of lakes,
rivers and oceans long ago.
• In general, the deeper the layer
(or stratum) from which the
fossil comes, the older the fossil
is.
• Some fossils can be dated by
radioactive materials in them.
The
Eons
of
Time
Eons
Eras
Periods
Millions of Years Ago
200
400
600
Phanerozoic
Eon (multicellular)
800
1000 (1 billion)
1200
1400
Cenozoic era
Quaternary, Tertiaray
Mammals
Mesozoic era
Cretaceous, Jurassic, Triassic
Reptiles, birds
Paleozoic
Permian, Carboniferous, Devonian
Fish
Silurian, Ordovician, Cambrian
Invertebrates
Neoproterozic
Proterozoic
Eon (eukaryotes)
Mesoproterozic
Neoarchean?
2000 (2 billion)
Archean Eon
2200
(prokaryotes)
3200
3400
3600
3800
4000 (4 billion)
Each era of the Precambrian can
be divided into several periods, but
they are not listed here because its
hard to fit them all in.
Eukaryotes?
Bacteria?
2600
3000 (3 billion)
and called the Precambrian
Meoarchean?
2400
2800
The periods that go before this
point are often lumped together
Paleoproterozoic
1600
1800
(what was going on)
Paleoarchean?
The starting point for
the Archean Eon has
been set at varios
points in this range
Most now put it at about
3.8 billion years ago
Hadean Eon
(no life)
Eoarchean
Heavy bombardment ends
Earth cools, Oceans form
Heavy comet bombardment!
Sun & Planets form
Geological Calendar
of the Phanerozoic Eon
Years ago
Era
Period (traditional)
Period (official)
Epoch
now
Cenozoic
Quaternary
Neogene
Recent, Pleistocene
Pliocene,
Miocene
Paleogene
Oligocene, Eocene
Paleocene
Cretaceous (K)
Cretaceous
Late Cretaceous ,
Early Cretaceous
144 million
Jurassic (J)
Jurassic
208 million
Triassic
Triassic
Late, Middle, and Early
Jurassic
Late, Middle, and Early
Triassic
Permian
Permian
Lopingian, Guadelupian
Cisuralian
286 million
Missisippian,
Pennsylvanian
Carboniferous
360 million
Devonian
Devonian
408 million
Silurian
Silurian
430 million
Ordovician
Ordovician
Pensylvanian,
Mississippian
Late, Middle, and Early
Devonian
Pridoli, Ludlow
Wenlock, Llandovery
Late, Middle and Early
Ordovician
505 million
Cambrian
Cambrian
Furongian, Middle, Early
Edicaron
Not used
2 million
Tertiary
35 million
65 million
245 million
550 million
Mesozoic
Paleozoic
Neoproterozoic
(Precambrian)
Evolution
• The idea that populations of organisms,
and therefore species of organisms,
change over long spans of time.
Next Slide: The first theory of evolution.
Lamarck’s Theory of Evolution
Jean Baptise Pierre Antoine de Monet Chevalier de Lamarck:
The guy with the big name and the wrong idea!(Perhaps)
• Lamarck first came up with a theory of
evolution (c.1802)
• Unfortunately his theory was wrong!
• Lamarck believed that organisms could
inherit “acquired characteristics” through
use and disuse.
– Lamarckian Myth: “If a giraffe stretches its
neck to reach leaves all its life, it’s offspring
will have longer necks.”
Lamarck’s reasoning…
• It seems sensible at first glance:
– Muscles that you use a lot grow larger, if you
don’t use them they atrophy (get smaller)
– It also makes sense that organs you don’t
need should gradually disappear
– Even some fossil record suggest that unused
organs may get smaller or eventually vanish,
(like human’s tail bone and appendix)
• The problem with Lamarck’s idea is the
mechanism he proposed. It doesn’t work!
Disproof of Lamarck’s Hypothesis
• If the idea of use and disuse were correct,
then preventing an organism from using a
structure for several generations would
cause that structure to atrophy (get smaller)
• Experiments have pretty much disproven
Lamarck’s hypothesis:
• If you remove the tails of mice, they cannot use them.
After several generations, mice with shorter tails
should be born, but this does NOT actually happen.
• Therefore, Lamarck’s main hypothesis is incorrect,
which makes his whole theory very unlikely…
But…
Perhaps Jean-Baptise Pierre Antoine de Monet
Chevalier de Lamarck was a little bit right!
• The recent science of epigenetics shows
that conditions during your lifetime can
switch genes on and off, and that some of
these changes may be passed on to
descendants.
In biology, the term epigenetics refers to changes in phenotype (appearance) or
gene expression caused by mechanisms other than changes in the underlying DNA
sequence, hence the name epi- (Greek: over; above) -genetics. These changes
may remain through cell divisions for the remainder of the cell's life and may also
last for multiple generations. However, there is no change in the underlying DNA
sequence of the organism; instead, non-genetic factors cause the organism's genes
to behave (or "express themselves") differently.
Charles Darwin and
Alfred Russel Wallace
• In 1858 two different people (Darwin and
Wallace) independently suggested a better
theory of evolution.
• Darwin published a more complete version
of the theory the next year*, along with
evidence he collected in the Galapagos
Islands, so he is generally credited with
the idea.
* On the Origin of Species by Means of Natural Selection, or the
Preservation of Favoured Races in the Struggle for Life, was published
November 24, 1859. Title was later shortened to The Origin of Species.
Darwin’s Hypotheses
• Descent with modification
– Organisms change slowly over
time.
– Newer species are the modified
descendants of older species.
• Modification by Natural
selection.
– The main reason that gradual
modifications occur is due to
Natural Selection.
Natural Selection
• The population of a species will increase
exponentially, until some environmental
factor limits it.
• When there is a limiting factor, not all
members of the species will survive to
reproduce.
– There is competition for food, space, mates etc.
– Only the members who are successful competitors
will survive to reproduce.
– The genetic traits that allow an organism to survive
are called its “fitness”.
– The survivors are said to be “adapted” to the
environment
The strength of Darwin’s Theory
• Darwin’s theories of evolution have been
rigorously examined for over 150 years.
• Although many minor changes have been
made to these theories to accommodate
new discoveries, the two most basic of
Darwin’s concepts continue to be valid:
– 1) That species change over time.
– 2) That the main cause of this change is
natural selection.
Internal Evidence of Evolution
(comes from studying the biology of organisms)
• Homologous Structures:
– Related organisms have structures that come from
similar sources* , (eg flipper of a seal and hand of human)
• Vestigial Structures:
– Organisms have the remains of organs that serve
little value at the present time (eg: human appendix
and “tail bone”)
• Similarities in Embryos:
– The embryos of different organisms look very similar
– “ontogeny recapitulates phylogeny”
• Similarities in DNA and proteins:
– Many organisms have similar biological chemicals
– DNA similarity is so closely linked to evolution that it
is now used trace the evolution of some organisms.
*don’t mix homologous structures with analogous structures, which are similar
in appearance but different in origin.
Haeckel’s Controversial
“Ontogeny Recapitulates Phylogeny” Drawing
Although
many of
Haekel’s ideas
have been
rejected by
modern
biologists as
oversimplified,
it is still a
fascinating
fact that the
fetus of an
organism
shows
evidence of its
evolutionary
ancestry.
External Evidence of Evolution
(comes from studies of other areas of science)
• The fossil record shows changes over time
– The organisms of today are different from the
fossils of the past
– The older the fossils are, the more differences
there are (in general).
• Changes in populations of species have
actually been observed in historic times.
– Eg. Manchester Peppered Moths.
The Peppered Moths
(Industrial Melanism)
• 1848 peppered moth
population near Manchester
• 98% light mottled moths
• 2% dark moths
• 1895
Clearly, some type of
• 5% light mottled moths
evolution is at work here.
• 95% dark moths
In just 50 years a rare
moth mutation has
become the typical
variety of moth.
Why ?
• If you were a bird who ate moths, which of the
moths in the picture below would you catch?
You would probably catch
the one that you can see.
In 1848, most of the trees
around Manchester were
covered in light lichens,
which camouflaged the
more common coloured
moths.
Easy to see
Harder to see
• During the 50 years that followed 1848, the
industrial revolution came to Manchester. The
lichens died from pollution, and the trees became
darker from soot. Now which moth would you
spot?
Easy to see
Harder to see
• Because the peppered moth population
change can be cited as proof that
evolution occurs, it has been very
controversial.
– Proponents use the extensive studies as
proof that the changes in a population can
occur as the result of natural selection.
– Opponents point out that the photos I showed
you were “staged”, therefore question if moths
would ever naturally settle on oppositely
coloured trees.
Patterns in Evolution
• Coevolution
– Two different organisms evolve in close relationship
to each other.
• Convergent Evolution
– Several different species adapt to the same
environment. Eventually they show similar features
(but they never become the same species)
• Divergent Evolution
– AKA Adaptive Radiation. One species adapts to fit
several different environments. Eventually it divides
into different species.
Chapter 16: Evolution of Populations
• In this chapter we will look at populations
and how they vary and how they spread
genes.
• We will look at mutations, and the effect
they have
• We will study speciation, the development
of new species.
Population Genetics
• Population genetics is the study of
evolution from a genetic point of view
• A population is group of similar organisms
Variation
• Within a population there is always
variation. Some organisms are a bit taller or
shorter, a bit faster or slower, a bit stronger
or weaker, etc.
Causes of Variation
• Environmental causes of variation
– Better food, growth conditions
– Injuries
Not so important
to evolution
• Genetic causes of variation
– Mutation (changes in genes)
– Recombination (separation of genes in
meiosis)
– Random breeding and fertilization
Hardy-Weinberg Principle
• Gene frequencies will not change if ALL of the
following are true:
–
–
–
–
–
No mutations occur (no radiation or mutagens)
There is no migration (no one leaves or arrives)
Population is very large (ideally infinite)
Individuals mate randomly (no preferential mating)
Natural selection does not occur (no competition)
• In other words, evolution would not happen in an
ideal world.
In the Real World, Evolution Occurs
• Mutations do happen
– Changes occur to genes as the result of
radiation, chemicals or random events
• Migration does happen
– Individuals arrive and leave populations,
changing the genetic makeup of the
population
• Populations are finite in size
– Small populations allow “genetic drift” to
occur, as allele frequencies change.
• Mating is not always random
– Some animals compete for mates, or have
rituals that determine who mates (eg. Only the
alpha wolf mates)
• Natural Selection does occur
– There is competition for resources in most
populations. The survivors are the ones who
reproduce.
Types of Natural Selection
• Stabilizing
– Most survivors are similar. The average is favoured,
unusual individuals seldom survive
• Directional
– Most survivors have a particular feature. Individuals
without the feature seldom survive.
• Disruptive
– Either of two extremes is favoured. Average individuals
seldom survive
• Sexual
– Mates are chosen by a particular feature. Individuals
without the feature seldom reproduce.
Chapter 17: Human Evolution
Hominid Fossils
• Humans and some of their extinct relatives
belong to a family known as hominids.
• Hominids are classed within the order
primates, along with apes and monkeys.
• The oldest hominid fossils have been
found in Africa.
“Lucy” a hominid fossil from
About 3 million years ago
• The complete classification of humans is:
– Kingdom Animalia (animal kingdom)
– Phylum Chordata (chordates have a notochord)
– Subphylum Vertebrata (with proper backbone)
– Superclass Tetrapoda (decendants of four-limbed
vertebrates)
– Class Mammalia (the mammals)
– Subclass Theria (live-birth mammals),
– infraclass Eutheria (placental mammals)
– Order Primates (the primates: monkeys, apes, hominids)
– Superfamily Hominoidae (anthropoids, greater apes)
– Family Hominidae (the hominids: humanlike. All other
hominids except humans are now extinct)
– Genus Homo (Humans and early humans)
– Species sapiens (Modern “wise” humans)
Some Identified Hominid Species
• Australopithicus afarensis “Lucy” is a
species found in the Afar valley of
Africa. They lived between 3 million
and 4 million years ago
• Australopithicus africanus, Taller
and heavier than “Lucy” lived in Africa
between 2.3 and 3 million years ago
• Paranthropus* robustus and
Paranthropus* boisei “nutcracker
man” both lived between 1 and 2
million years ago in Africa
* These two were formerly placed in genus Australopithicus
Australopithicus
Paranthropus
A newly identified hominid
• Ardipithicus ramidus (Ardi): a chimpanzee
sized hominid found in Africa and dated to about
4.4 million years, making it the oldest nearly
intact hominid skeleton ever found.
On October 1, 2009, paleontologists formally announced the discovery of
the relatively complete A. ramidus fossil skeleton first unearthed in 1994.
The fossil is the remains of a small-brained 50-kilogram (110 lb) female,
nicknamed "Ardi", and includes most of the skull and teeth, as well as the
pelvis, hands, and feet
More Identified Hominid Species
• Homo Habilis “Handy Man” lived in
Africa about 2.5 million years ago. This
fossil used tools and may be the
earliest representative of the human
genus.
• Homo Erectus, “upright human” was
first discovered in Java (nicknamed
Java man), and since then all over
Asia, Africa and Europe. This may well
be the ancestor of modern humans.
They existed from 1.8 million years ago
to as recently as 40,000 years.
Two Modern Human Species
• Homo neanderthalensis (or possibly
Homo sapiens- neanderthalensis) lived in
Europe from about 1.8 million years ago
to as recently as 30,000 years ago. It
has not been established if this was a
separate species of human, or a “subspecies” that would be capable of
breeding with “modern” humans (hence
the disputed classification)
The most recent evidence is that these two types of
human were different species, so I will use the terms
homo sapiens and homo neanderthalensis
• Homo sapiens (or perhaps Homo sapiens
sapiens) is the designation of modern
humans. The first fossils of modern
humans were found in the Cro-magnon
caves in southern France.
Because of where they were first found, early
homo sapiens are occasionally referred to as
“Cro-magnon man”. This is not an official
designation, as they were undoubtedly the
same species as modern man.
Some lesser-known and disputed
hominid fossils
• Homo Floresiensis? “hobbit”: a very small
hominid fossil recently found in Malasia dating to
about 13000 years ago. Its authenticity is still
under dispute. It may be a malformed human.
• Homo Heidelburgensis “Goliath” is a large fossil
homind found in Germany. It may be a separate
species or a variety of Neanderthal, Homo
Erectus or Antecessor
• Homo Antecessor is a fossil found in Spain
which may be an ancestor of both Neanderthals
and modern humans, or it may simply be a
variety of Neanderthal or Homo Erectus
Homo Sapiens
Homo Habilis
Homo Erectus
(Homo Floresiensis)
(Homo Heidelbergensis)
Paranthropus Boisei
Neanderthal
Probable Brain Sizes
500 cm3
700 cm3
1000 cm3
He thinks
He’s so
Smart!
1450 cm3
1400 cm3
Chapter 18: Classification
• What is a species?
• What is Taxonomy?
• What was Linnaeus’ System and the
seven original levels?
What is a species?
• Textbook definition:
“A species is a group of organisms of a single
type that are capable of producing fertile
offspring in a natural environment.”
• But all definitions of species are
controversial, especially for extinct species
where we cannot test breeding ability.
– Everybody accepts the idea that members of
the same species look similar and can mate
with each other. The problems are in the
details– How similar? How successful is the
mating? How productive are the offspring?
What is Taxonomy?
• Taxonomy is the science of classifying
things. In biology this refers to organizing
species into different groups.
• This can sometimes be quite difficult.
– Taxonomists often make judgement calls
when grouping organisms into categories.
Other taxonomists may later disagree and
reclassify the organisms.
Who was Linnaeus and what was
his system?
• Carolus Linnaeus (1707-1778) was a Swedish
scientist who grouped living things into
hierarchical categories.
– “hierarchical” means at different levels
• The seven levels Linnaeus created were:
–
–
–
–
–
–
–
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
Highest level, eg. Animals (vs. plants)
2nd level: eg. Chordates (vs. invertebrates)
3rd level: eg. Mammals (vs. reptiles, birds, fish)
4th level: eg. Carnivores (vs. marsupials, whales)
5th level: eg. Canines (vs. cats, seals, weasels)
6th level: closely related species, eg. wolf & dog
most specific level, eg. Canis familiaris
Binomial Nomenclature
• Linnaeus also introduced the method of
scientific naming called binomial
nomenclature.
– He identified each organism by using a
combination of its Genus and Species name.
– He made sure that no two creatures had the
same combination of genus & species name.
– He used Latin (widely read by educated
people at that time)
– The genus name was always a Latinized
noun, the species name was a Latin adjective.
Categorizing Life
• Linnaeus based his system on observable
characteristics, and assumed that seven
levels would be enough.
• Since then we have added many other
ways of grouping organisms, including:
– Systematics (Phylogeny) – Organized on the
basis of evolution, using phylogenetic trees
– Cladistics – Organized on the basis of derived
characteristics, using cladograms
– Genetics – Organized on the basis of
similarities in DNA
A Phylogenetic Tree
• A phylogenetic tree
shows the presumed
relationship between
organisms and their
common ancestors
• See another example
on page 343
Cladogram
• A cladogram is
similar to a
phylogenetic tree,
but each division is
limited to two
branches based on
a specific derived
feature.
• Another example on
page 346
Genetics (DNA)
• Study of the similarity of DNA of
organisms allows geneticists to estimate
the time since two organisms had a
common ancestor.
• For example, humans and chimpanzees
had a common ancestor about 5 million
years ago, based on DNA similarity.
– When all we had were fossils, most
palaeontologists assumed humans & chimps
diverged 25 million years ago. Now we
believe it was much more recent.
How many kingdoms?
• Since Linnaeus’ time there has been
frequent debate about how many
kingdoms are needed…
• Linnaeus recognized two: plants & animals
• Later, we separated the fungi from plants
• When microscopic organisms were
discovered we added kingdom protista.
• With bacteria we first added monera,
• But then divided monera into eubacteria
and archaebacteria
Development of Kingdoms
from 1735-2000
Linnaeus
1735
2
kingdoms
Haeckel
1866
3
kingdoms
Protista
Chatton
1937
2
empires
Prokaryota
Eukaryota
Vegetabilia
Animalia
Woese etc.
1990
3
domains
Cavalier-Smith
Eubacteria
Bacteria
Bacteria
archeabacteria
Archaea
(Archeabacteria)
Protista
Protista
Eukarya
Protozoa
Fungi
Fungi
Chromista
Plantae
Plantae
Plantae
Fungi
Animalia
Animalia
Animalia
Copeland
1956
4
kingdoms
Mychota
Protoctista
Plantae
Animalia
Whittaker
1969
5
kingdoms
Monera
Woese etc.
1977
6
kingdoms
2004
6
kingdoms
Plantae
Animalia
Optional Enrichment
Carl Woese and the importance of microscopic life.
•
Carl R. Woese is famous for shaking up our idea of kingdoms in the 1980s. While
studying the ribosomal DNA of bacteria he became convinced that there was an
important division within bacteria that occurred long before the rise of eukaryotic
cells. He suggested that life should be divided into three domains instead of six or
seven kingdoms. Even today, his research remains controversial, but it does point
out that evolution was important to early bacteria.
Many biologists now add his
domains as an extra level of
classification above kingdoms
Woese’s
tree of life.
The Six Kingdoms
• Kingdom Archaebacteria (AKA.
Archae, formerly part of Monera)
– Unicellular, prokaryotic bacteria of
ancient origin
– Include methanogenic and
chemosynthetic organisms
• Kingdom Eubacteria (AKA. Bacteria,
formerly part of Monera)
– Unicellular, prokaryotic bacteria of
more recent origin.
– Include most common bacteria.
• Kingdom Protista (the “protists”)
– Eukaryotic organisms (have cells with true
nucleus and organelles)
– Most are single celled and microscopic
• but some are multi-cellular but with little
differentiation, including a few very large seaweeds
• Most are heterotrophs, meaning they feed on other
organisms (the protozoa); but a some are
photosynthetic autotrophs with chlorophyll (the
algae)
Proposed Change to Kingdom Protista
c. 2004
• It has been said that kingdom protista had
become a dumping ground for all
organisms that don’t belong to one of the
other kingdoms, so in 2004 it was
proposed to divide it into 2 kingdoms.
• Kingdom Protozoa: the animal-like protists
• Kingdom Chromista: the algae and
seaweeds (plant-like protists).
Why are giant seeweeds considered to
be protists (or perhaps chromista)
instead of plants?
• Seaweeds look like plants and have many
features of plants
– They have photosynthesis and are greenish
– They are multicellular
– They have cell walls and large vacuoles
• But… biologists now think that they evolved
separately from plants
– They both came from simple algae, but along different
branches of a phylogenetic tree.
– Seaweeds have fewer tissues or organs than plants
– Genetically, seaweeds are closer to algae than to
plants
• Kingdom Fungi (all the fungus)
– Heterotrophic (no photosynthesis)
– Unicellular and multi-cellular (microscopic to
very large)
– Most have cell walls (like plants) but lack
chlorophyll. Many are multi-nucleate.
– Includes molds, mildews, rusts, smuts,
mushrooms, puffballs, morels, truffles, and
any other types of fungus.
• Kingdom Plantae (the plants)
– Nearly all plants are
autotrophs (make their own
food)
– Multi-cellular, and some can
grow quite large. (100m tall
Sequoias and Douglas firs)
– Nearly all plants use
photosynthesis as their main
source of food.
• Pitcher plants and Venus Fly
Traps get extra nutrients from
insects.
• Kingdom Animalia (the animals)
– Multicellular organisms
– Heterotrophic (they eat other food)
– Varied body types, including:
• Sponges, jellyfish, worms, mollusks (clams,
squids, snails) worms, arthropods (including:
crabs, spiders, insects), vertebrates (including:
fish, amphibians, reptiles, birds, mammals)
The Domain System
• Some taxonomists have suggested that we
replace Linnaeus’ system of kingdoms with three
“Domains”
– Domain Bacteria (= Kingdom Eubacteria)
– Domain Archaea (= Kingdom Archaebacteria)
– Domain Eukarya (Plants, Animals, Fungi, Protists)
• So far, this has NOT caught on!
Archeabacteria
Eubacteria
Current system Δ
Archaea
Bacteria
Protista
Fungi
Plantae
Animalia
Proposed system▼
Eukarya
Extra Levels of Taxonomy
(don’t try to memorize)
Magnorder
Domain
Superkingdom
Superphylum
Superclass
Superorder
Superfamily
Superspecies
Kingdom
Phylum or
Division
Class
Order
Family
Genus
Species
Subkingdom
Subphylum
Subclass
Suborder
Subfamily
Subgenus
Subspecies
Branch
Infraphylum
Infraclass
Infraorder
Infrafamily
or Tribe**
Microphylum
Parvclass*
Parvorder
Alliance**
Infraspecies
Exercise
• Using the keys on pages 1092-1099, classify the
following organisms:
–
–
–
–
–
–
–
–
–
–
A duck
A mushroom
A seahorse
A snake
A rose
A moss
An oyster
An octopus
A wasp
A lobster
For some you can just find kingdom and phylum, some you can
classify down to order.
Classification
kingdom
Phylum
Class
Order
Animalia
Chordata
Aves
Anseriformes
Fungi
Basidiomycota
Basidiomycetes Agaricales
Animalia
Chordata
Osteichthyes
Sygnathiformes
Animalia
Chordata
Reptilia*
Squamata
Plantae
Anthophyta
Dicotyledones
Rosales
Plantae
Bryophyta
Bryidae
Polytrichales
Animalia
Mollusca
Bivalva
Filibranchia
Animalia
Mollusca
Cephalopoda
Coleoidea
Animalia
Arthropoda
Insecta
Hymenoptera
Animalia
Arthropoda
Crustacea
Decapoda
*in some taxonomies, Reptilia has been replaced by Sauropsida
The Reptile vs. Bird Controversy
Should reptiles and birds be separate classes? According to cladistics, no, but
according to systematics (phylogeny) and tradition, yes they should.
The trouble, it turns out, is that birds are far more closely related to reptiles than
we used to think, but most people still don’t want to call birds reptiles!
Most people still use the term “class reptilia” for reptiles and “class aves” for birds,
but a few taxonomists use “class sauropsida” for both birds and reptiles together.
Bird vs. Reptile
PhyloCode
• A new system of taxonomy, called International
Code of Phylogenetic Nomenclature, or
PhyloCode for short, is currently being drafted.
• It is intended to replace the Linnaean system
that we have used for the last 250 years with a
new way of looking at taxonomy.
• The current system will continue to exist as a
“rank based system” for a long time to come.
• PhyloCode is currently in its fourth draft, and it has not yet
been implimented. For the text of the fourth draft visit the
website: http://www.ohio.edu/phylocode/toc.html. Although it
will soon be used by biologists, it is unlikely to ever be used
widely by the general public.