introduction to evolutionary mechanisms

how old is the earth?

~4.6 billion years old

What are the four eons, from oldest to most recent

Haden —>Archean —>Proterozoic —>Phanerozoic

When was the hadean eon? Name 1 major event that occurred during the hadean?

• The hadean was 4.6 - 4.0 billion years ago

• During the hadean eon, the Earth was formed, and was likely too hot to sustain any life

When was the archaean eon? Name 2 major events that occurred during the archaean?

• The archaean was 4.0 - 2.5 billion years ago

• During the archaean eon, the earth cooled enough to sustain life, and the first prokaryotic life appeared

When was the Proterozoic eon? Name 4 major events that occurred during the Proterozoic?

• The Proterozoic was 2.5 - 0.541 billion years ago

• During the Proterozoic eon, the first eukaryotes, metazoans and soft bodied animals appeared

• The oxygen revolution, snowball earth and the boring billion

Oxygen revolution/ the great oxidation event

Cyanobacteria converted mass amounts of CO2 into oxygen, but there was nothing to convert the O2 back into CO2, leading to a mass extinction of cyanobacteria and the evolution of the first eukaryotes

Snowball earth

A series of repeated ice ages so extreme that from space, the completely frozen surface of earth may have looked a snowball (worsened by excessive oxygen in the atmosphere)

Boring billion

Period of a billion years during the Proterozoic eon where no major events occurred except for the evolution of multicellular eukaryotes like metazoans and soft bodied animals (like jellies)

When did the Phanerozoic eon begin?

• The Phanerozoic began 541 million years ago and has continued to the present

What are the three eras of the Phanerozoic eon?

1. Paleozoic (541mya to 252mya)

2. Mesozoic (252mya to 66mya)

3. Cenozoic (66mya to present)

What are the four measures of time from largest to smallest?

Eon → Era → Period → Enoch

what are the 6 periods of the paleozoic era?

cambrian, ordovician, silurian, devonian, carboniferous, permian

what are the three periods of the mesozoic era?

triassic, jurassic, cretaceous

what are the three periods of the cenozoic era? name the epochs for each period in order

paleogene (oligocene, eocene, paleocene), neogene (miocene, pliocene), quaternary (pleistocene, holocene)

major events of the paleozoic

major events of the mesozoic

Rise of the gymnosperms, age of the dinosaurs, origin of flowering plants, first birds, mammals

major events of the cenozoic?

radiation of whales, primates and mammals

what covered Manitoba and most of North America during the late Cretaceous?

the western interior seaway. this is why there are so many fossils found in deserts and other seemingly random places today

what types of species is the fossil record biased towards?

organisms that had hard parts, were widespread and existed for a long time

what are stromatelites? (Shark Bay, Australia)

banded/layered rocks that arose from the activities of certain prokaryotes in the archaean eon, giving us evidence that there were prokaryotic cells at least 3.5bya

during which period did eukaryotes (unicellular and multicellular) arise? when does the oldest unicellular eukaryotic fossil date back to?

both unicellular and multicellular prokaryotes originated during the proterozoic eon. the oldest unicellular eukaryotic fossil dates back to ~1.8 billion years ago

Burgess Shale

a famous fossil site in Yoho National Park (BC) containing fossil evidence of many Cambrian soft bodied animal life produced during the Cambrian explosion (including trilobite fossils, and our ancestor the pikaia)

what are the five major extinction events? during which periods did they take place?

ordovician (end of ordovician), devonian (end of Devonian), permian (end of permian, biggest mass extinction, “planet killer”), triassic (end of triassic), cretaceous (end of cretaceous, meteorite crashed into Mexico, extinction of dinosaurs except birds)

what is our earliest known chordate ancestor that lived during the Cambrian?

Pikaia

when did tetrapods first appear?

the Devonian period (paleozoic era, phanerozoic eon)

how did mammalian jaws develop from the Synapsid differently from the reptile jaw?

• the Synapsid, a descendent of the tetrapod ancestor leading to both reptiles and mammals had a quadrate-articular jaw hinge

• in early cynodonts (and later, mammals), this later evolved into a dentary-squamosal jaw hinge

• in mammals, the quadrate and articular bones are now part of the mammalian ear

continental drift

the process by which the continental plates move over the underlying mantle. plates can collide, separate or just slide past each other, and these interactions lead to morphological changes on the earth’s surface

1. at how many points in time was there a supercontinent on earth?

2. what is the most recent time? what was the supercontinent called?

3. what happened to this supercontinent at the end of the Jurassic?

4. the breakup of this supercontinent led to __ (allopatric, sympatric) speciation

1. three

2. 250 million years ago during the Permian, known as Pangaea

3. it split into Laurasia and Gondwana

4. allopatric

what are 4 of the impacts of the formation of pangaea had on the environment?

1. there was a reduction in shallow water climates (where many marine organisms lived)

2. the climate inland became colder and dryer

3. there were general changes in climate especially for planets moving away from or closer to the poles

4. changes in ocean circulation patterns (currents) lead to global cooling

what is a mass extinction event?

the rate of extinction increases dramatically, causing a mass extinction event during which more than 50% of the species on earth become extinct

Permian mass extinction

a) when was it?

b) what caused it?

c) what types of species in particular went extinct?

a) 252 million years ago, defining the boundary between the Paleozoic and Mesozoic eras

b) volcanic activity in the Siberian traps, leading to global warming, ocean acidification and a decrease in oceanic oxygen

c) because the ocean was turned into “hot acidic soup” with only a few habitable areas, ~96% of marine species along with many terrestrial species

Cretaceous mass extinction

a) when was it?

b) what caused it?

c) what types of species in particular went extinct?

a) 66 million years ago, separating the Mesozoic from the Cenozoic

b) likely caused by a massive meteorite that landed in the Yucatan Peninsula near Mexico

c) almost all dinosaurs except birds and half of all marine species in addition to many terrestrial plants and animals

what are adaptive radiations

periods of evolutionary change during which organisms diversify rapidly into many new species, often due to new ecological opportunities (ex. many new ecological roles open up after a mass extinction)

when did mammals undergo an adaptive radiation and why?

mammals underwent an adaptive radiation following the cretaceous mass extinction because the extinction of dinosaurs created new roles mammals could fill without competition

what is heterochrony?

evolutionary change in the rate or timing of developmental events including reproductive development which can have significant impacts (ex. Shapes of chimpanzee and human skulls are a result of heterochrony)

what is phaedomorphosis?

due to heterochrony, reproductive development occurs faster than other development, leading to sexually mature species with other juvenile structures

what are homeotic genes? provide two examples of things homeotic genes could control

homeotic genes are genes that when mutated can cause significant evolutionary change due to their role in controlling placement and organization of body parts. Ex. Where wings and legs develop on a bird, how flower petals are arranged

is evolution goal oriented?

no, evolution is not goal oriented but more so

what are the four supergroups of eukaryotes?

excavata, SAR, archaeplastida and unikonta

groups and subgroups of excavata?

diplomonads (ex. giardia tintestinalis), parabasilids (ex. yeast infection), eugenazoans (euglena, kinetoplastids (trypanosoma))

groups and subgroups of SAR

stramenopiles (brown algae, diatoms), alveolates (apicomplexans (ex. plasmodium causes malaria), ciliates, dinoflagellates) and rhizarians

when did plants colonize land? what is the closest living relative of land plants?

during the ordovician, charophytes

what 3 key traits are present in almost all embryophytes but are absent in charophytes?

alternation of generations, production of walled spores in sporangia, apical meristems

sporopollenin

durable material found in the walls of haploid spores in embryophytes and zygotes in charophytes

Explain Darwin and population thinking

Darwin knew that all individuals in biological populations vary, and that no two are identical. This variation is used by natural selection as a source of evolutionary novelty