Early Animal Evolution

Question 1

total species

Answer 1

1,740,300 but number is iffy as what is considered a species is being debated

prokaryotes number can very from 10k-1000k deoending on classification

Insects have the most species

Humans/mammals have 5490 species

Question 2

Endosymbiosis

Answer 2

Two organisms living with one inside the other

Question 3

Green and Ice house states

Answer 3

Icehouse state is when there are glaciers present at both poles and the earth oscillates between glacial and interglacial periods

Greenhouse state is when the glaciers have melted

Question 4

Synapsids

Answer 4

Mammal like reptiles that gave way to the rise of archosaurian reptiles (dinosaurs)

Question 5

The Great Oxidation Event

Answer 5

• Cyanobacteria are oxygenic phototrophs
• Cyanobacteria introduced oxygen into the atmosphere over 200-300 million years displacing methane
• This likely led to a global extinction of many anaerobic taxa from the now poisonous oxygenated atmosphere
• oxygen begins to concentrate in the atmosphere; aerobic metabolism; early eukaryotic cells; protists, fungi and soft-bodied animals
• development of the electron transport chain from endosymbiosis
• complete oxidation of glucose to CO2 and H2O to produce ATP
• Fuel efficiency promotes multicellular creatures

Question 6

Cambrian Explosion

Answer 6

• Beggining of Cambrian
• Rapid diversification of animals
  -Fossil record shows early evolution of arthropods, mollusks, and fish
• Some species were classified as “problematica” because scientists couldn’t discern which way was up or down
• This period was precipitated by an increase in oxygen levels that likely coincided with an increase in algal abundance (food)

Question 7

Late Ordovician Mass Extinction

Answer 7

First of the “big five” mass extinctions
~estimated extinction of 53% to 85% marine species
Divided into two pulses of extinction
LOMEI-1: cooling resulting in an icehouse state (as opposed to a greenhouse state)
Icehouse state is when there are glaciers present at both poles and the Earth oscillates between glacial and interglacial periods
Sea levels drop significantly during icehouse
Loss of marine habitats (along coastal regions)
Marine fauna diversified to adapt to the cold-water habitats
The Great Ordovician Biodiversification Event resulted in an increase in global diversity associated with increase in O2 (algae invade land and become plants)
LOMEI-2, the second pulse, resulted from rapid warming (icehouse back to greenhouse) – anoxia leading to loss of marine invertebrate diversity

Question 8

Paleozoic land invasions and animal diversifcation

Answer 8

Land animals came late to the party
By 400 million years ago land plants were well established with shrubs, trees (early conifers and fern-like trees)
Late Devonian mass extinction
Second of the “big five”
~70% of all species extinct
Indicates mass loss of calcite-based reef builders
~0.5 billion years ago to present – development of oxygen delivery system - 450 MYA hemoglobin evolved - allowed animals to grow more because of diffusion of oxygen

Question 9

Permian Triassic Boundary

Answer 9

Third and biggest of the “big five” mass extinctions
Loss of ~80 % of all marine species
Loss of 70% of terrestrial vertebrates including the largest extinction event for insects
CO2 levels rose from 400 pm to 2,500 ppm and temperatures rose 8°C
Also called the “Great Dying”
286 of the 329 marine invertebrate genera disappear from the fossil record

Marine vertebrates were more susceptible to exctinction – ocean acidicfication – co2 absorbs easily into the ocean

Marks a change in animal fossils between the Paleozoic and Mesozoic Eras
Mammal-like reptiles called synapsids give way to the rise of archosaurian reptiles (dinosaurs)
Start of the Triassic begins with the “coal gap” (a lack of plant matter decaying into peat) which may indicate that it took several million years for ecosystems to reestablish themselves

Question 10

Mesozoic

Answer 10

Development of compex vasuclar/ respiratory systems
Frogs mammals etc evolved durng mesozoic
Land vertebrates were dominated by the dinosaurs
An extinction event bottlenecked the non dinosaur groups at the end of the triassic
Led to ana adpative radition of dinosaurs (the rapid diversification of new forms)

Question 11

Adaptive Radiation

Answer 11

rapid diversiifctaion of new forms

Question 12

Triassic Jurassic Exticntion event

Answer 12

Most of large amphibians became extinct allowing for terrestrial dinosaurs to have little competition
Fourth mass extinction event
Most of early arhcosauromorpha went extinct

Question 13

K-Pg extinction

Answer 13

KT extinction
Fifth extinction
Extcion of nonavian dinosaurs
Asteroid impact the yucatan mexico
gave rise to mammalian and bird groups

Question 14

Great Mammalian radiation

Answer 14

rapid increase in szie and behaviour cnages within mammalia
Switch from nocturnal to diurnal
Taxonimci richness doubles
Size rapidly increases among mammals and by 700k mammal are 50kg and benefitting from the emergence of beans
Size increases happened in bursts with coinciding warm periods
wamring periods promoted plant growth and provided nutrients for larger aniamls
Coevolution
Fleshy fruits started to appear and coincide with the diversifcation of plesiadapiforms or ancestral primates - mammals were great seed dispersers

Question 15

Coevolution

Answer 15

The reciprocal evolutionary changes in two or more taxa as the consequence of their interactions applying selective pressures

Question 16

Glaciations

Answer 16

over last 1.8 m years, northern regions have undergone glaciations
During glaciations, much of earths water is frozen
Caused sea leevls to drop 400’
Land was uncovered and became bridges between continets that allowed humans and animals to migrate

Wisconsinan Glaciation:
Covered most of northern half of NA from 85k to 7k years ago
Recent glacial maxium was 21,000 ybp
Some areas only recently deglaciated and some are still covered

Question 17

Pleistocence Megafauan Extinctions

Answer 17

Overkill hypothesis: humans were responible of exticntion of megafauna
Climate change resulting form the end of the last glaciation resulted in massive ecosystm alteration and megafauna extinction