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DIVERSITY OF LIFE
Current species are classified into 3 Domains and/or 5-6 Kingdoms
Kingdoms
1. Prokaryotes
2. Protists
3. Plants
4. Fungi
5. Animals
Domains
1a. Archaebacteria
1b. Eubacteria
Archaea
Bacteria
Eukarya
Major groups are related
All alive today
All equally “evolved”
But also represent
different depths of
branching, time
since shared
common ancestor
Diversification also
involved a series of
innovations that added
new forms of life
Older modes persisted,
possibly largely
unchanged
“advanced” vs. “primitive”
Diverse species
appeared then went
extinct
Current diversity is a
slice of a continuing
process
3-1
1. Prokaryotes (bacteria)
single celled
DNA, lack nucleus
no organelles
motility, incl. flagella
closest to early life?
Prokaryotes
No sexual reproduction (meiosis)
per se, but various modes of
genetic exchange
The real “tree” of life?
Prokaryotes
Much of biochemistry evolved in this group
Both respiration and photosynthesis started here
__________ (“self feeding”) – use CO2 as carbon source
chemoautotroph – energy from chemicals (e.g. H2S)
photoautotroph – energy from sun - photosynthesis
___________ (“other feeding”)– use organic molecules for
carbon and energy
anaerobic – respiration without O2
aerobic – respiration with O2
Prokaryotes
Cyanobacteria (“blue-green algae”) are free living
and photosynthetic
contain chlorophyll a, ancestor of __________
Prokaryotes
Some bacteria and cyanobacteria can also fix ________
In aquatic and
terrestrial systems
Even in some plant roots
Also involved in other Nitrogen transformations (discussed later)
Important as ________________
and Pathogens
Often closely related species
Prokaryotes
Archaea – extreme environments – salty, high temperature
Prokaryotes
“Black smoker” (hydrothermal vent)
http://www.ocean.udel.edu/kiosk/bsmoker.html
Archaea – “ancient”,
origin of life?
Eukaryotes – Protists, Plants, Fungi, Animals
_________ and Endomembrane
Organelles – mitochondria and chloroplasts
Sexual reproduction (meiosis)
Multicellularity (tissues, organs)
Sociality
2. Protists – mostly small, single celled & multicellular
- Eukaryotes – true nucleus (containing DNA) and endomembrane
- Many are heterotrophs, aquatic – highly diverse
- Various parasites (e.g., amoebas, malaria, helminths)
Endosymbiotic origin of organelles
Mitochondria - ___________
Chloroplast - ___________
Key biochemistry done by bacteria or their descendants
Protists
Includes true ALGAE – single and multicellular forms that
are photosynthetic, and mainly ________(main “producers”
in _________ systems)
Unicellular algae
- contain chloroplasts
- chlorophyll a, b, & c
Multicellular algae – “___________”
- various differentiated structures, food
conducting systems
- not rooted - holdfast (nutrients from water)
Complex life cycles & Sexual Reproduction
Both diploid and haploid phases
Sexual (meiosis) and
asexual (mitosis)
components
Brown Alga (Laminaria)
Green Alga (Ulva) – haploid & diploid equivalent
What is Diploid? Haploid?
Life cycles often switch between these two states.
___________ are haploid and fuse to form diploid zygotes.
The zygote is “diploid” because it contains two complete
sets of genes, one “haploid” set from each parent. This
means two copies of genes of each gene type (“locus”).
The two copies need not be identical (alternate “alleles”
are common at each locus)
What is Meiosis? Mitosis?
When a phase of the life cycle duplicates itself asexually, it
is a result of mitosis – the exact copying of the genes.
Meiosis
Sexual reproduction results
from a much stranger process,
where the diploid produces
haploid cells by meiosis. The
genes replicate once, then
divide twice, creating (four)
cells with only one set of genes
each (haploid).
Both haploids and diploids can replicate asexually (mitotically) too
“Water Mold” (Oomycota) – mostly diploid
Malaria (Plasmodium)
mostly haploid
Recombination – the real point?
At least as important as the production of haploid cells, is
the recombination of alleles in meiosis. Before making
haploid cells, the dividing cells undergoing meiosis
essentially “shuffle” the two parental genotypes, creating
new genotypes that are mixtures of the parents. Often, the
resulting recombinant haploid gametes are fused with
gametes from other individuals (___________) to make the
zygotes. This creates new genetic variation. The offspring
are different from each other and from either parent.
Independent assortment
Shuffling whole chromosomes
(chromosomes = blocks of genes)
Crossing over
Shuffling genes
within chromosomes
The paradox of sex - why meiosis?
We have emphasized that evolution favors organisms
(autocatalysts) that are good at transforming resources into
more self – but here is a widespread mode of reproduction
that seems designed to create offspring that are different
from the parents, that are deliberately NOT self.
Why? It is assumed there are good reasons, we just
don’t know what they are for sure. But of course there have
been many proposed explanations (hypotheses).
This is another good example of the difficulty of
verifying functional explanations.
The Main Contenders
1.
a.
b.
2.
a.
b.
3.
4.
5.
3. Plants
- primarily terrestrial, multicellular
- evolved from ________________
- photosynthetic (chloroplasts), rooted in soil (nutrients)
- extensive _____________ tissue
- widespread, diverse
Mosses and related species
Ferns and others
Includes tree ferns, once dominant
Petro future here
Coal Age – Carboniferous 290-360 MYBP
How long will current oil supplies last?
= _______ years
http://www.eia.doe.gov/oiaf/ieo/oil.html
Gymnosperms (conifers and others)
Ginko
Cycad
Welwitschia
Read Sacks
Conifers
Angiosperms – flowering plants
Include most plants that dominate landscapes today
4. Fungi
- eukaryotic, diverse ____________
- unicellular (yeast) and multicelled (mushrooms)
- with bacteria, the most important _________ (nutrient
releasers) in aquatic and terrestrial systems
Read Sacks
4. Fungi
- important __________, plant root
fungal symbionts that enhance
nutrient and water uptake
- many fungi are plant & animal
pathogens (mostly plants)
4. Fungi- include photosynthetic _______ – a symbiotic
association of a fungus and a green algae. Fungus gets
carbohydrates for photosynthesis of algae. Live on bare
substrate (rock, bark), tolerate drying.
Largest organism?
Blue Whale
Giant sequoia
Aspen clone (Populus
tremuloides) – one genotype
Honey mushroom (Armillaria ostoyae) – one genotype
5. Animals
- evolved from ________
- multicellular,
heterotrophic eukaryotes
- 35 “body plans”, most
invertebrates, many marine
- highly elaborated tissue
and organ systems
- herbivores, carnivores,
parasites
Sponges
Jelly
Anemone
Chiton (Mollusk)
Rotifer
Scallop (Bivalve)
Sea Slug (Gastropod)
Sea Star
Cephalopods: Nautilus & Octopus
Leech (Annelid)
Corals - _______________
- have a symbiotic association
with “zooxanthellae” which are
themselves a symbiosis of a
dinoflagellate (protist) and
photosynthetic cyanobacteria
(prokaryote).
Arthropods
Trilobite (extinct)
Barnacle
Shrimp
Horseshoe Crab
Lobster
Trilobite Optics
Trilobites developed one of the first advanced visual
systems in the animal kingdom. This may have promoted
the spectacular diversification of animals.
The majority of
trilobites bore a pair
of compound eyes
(made up of many
lensed units)
Compound eyes in living arthropods such as
insects are very sensitive to motion, and it is
likely that they were similarly important in
predator detection in trilobites. It has also been
suggested that stereoscopic vision was provided
by closely spaced, but separate eyes
http://www.trilobites.info/eyes.htm
http://ebiomedia.com/gall/eyes/octopus-insect.html
Some Trilobites “lost” vision, as have many existing species
crayfish
Astaynax
Yamamoto Y, Stock DW, Jeffery WR (2004) Hedgehog signalling
controls eye degeneration in blind cavefish. Nature 431:844-847.
The eyes of the Octopus and Squid (Cephalopods) are
very similar to ours in structure and function, with lens
and image forming retina.
Read Williams
Eyes of the vertebrates and cephalopod molluscs (squid and octopus) are
remarkably similar, an example of ___________evolution. One interesting
difference – vertebrates have an inverted retina, the sensory cells lying beneath
the nerve fibers. This results in the sensory cells being absent where the optic
nerve is attached to the eye, thus creating a blind spot. The octopus eye has a
non-inverted retina in which the sensory cells lie above the nerve fibres. There is
therefore no blind spot in this kind of eye.
http://en.wikipedia.org/wiki/Evidence_of_evolution
The Blind Spot The blind spot is the area on the retina without
receptors that respond to light. Therefore an image that falls on
this region will NOT be seen. It is in this region that the optic
nerve exits the eye on its way to the brain.
In the next two images, close your right eye. With your left eye, look at the numbers on the right side, starting
with the number "1." You should be able to see the "sad face" (top image) or the gap in the blue line (bottom
image) in your peripheral vision. Keep your head still, and with your left eye, look at the other numbers. The
sad face should disappear when you get to "4" and reappear at about "7." Similarly the blue line will appear
complete between "4" and "7.“ This is because your brain is "filling in" the missing information.
Here is another image to show your blind spot. Close your right eye. With your left eye, look at the +. You should
see the red dot in your peripheral vision. Keep looking at the + with your left eye. The red dot will move from the
left to the right and disappear and reappear as the dot moves into and out of your blind spot.
http://staff.washington.edu/chudler/chvision.html
Arthropods – Spiders and Insects
Vertebrates (Chordates)
Animals - Sociality
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