Macroevolution

Question 1

Ecological Opportunity

Answer 1

Hawaiian honeycreepers - radiated to 54 species, filled niches, others species arrived after honeycreepers (Thrushes and Flycatchers) did not radiate bc niches were already filled

Question 2

Ecological Opport.

Answer 2

Mammals radiated 65 mya; following ext. of dinosaurs

Question 3

__________ is facilitated by the availability of unfilled niches

Answer 3

Adaptive radiation

Question 4

Criteria for adaptive radiation

Answer 4

Common ancestry, divergence of traits related to performance (individuals in different habitats evolve different characteristics that allow them to thrive in those unique conditions, often driven by a form of natural selection called “diversifying selection” (or disruptive selection) where extreme phenotypes are favored over intermediate ones), rapid speciation

Question 5

Example of adaptive radiation

Answer 5

Darwin’s Finches;
common ancestry, rapid speciation, trait divergence (beaks)

Question 6

2 causes of adaptive radiation?

Answer 6

1. Ecological opportunity (availability of unfilled niches)
2. key innovations

Question 7

Innovation - novel adaptation that opens up adaptive zone

Answer 7

Jointed limb in arthropods (insects, crustaceans, spiders, etc.)

waxy cuticle and stomata in aquatic plants facilitated the colonization of land, and lead to a radiation of land plants ~400 mya

Flight in birds, bats, and insects

Question 8

Mass extinction

Answer 8

K-Pg - 60-80% of species extinct; dinosaurs, marine reptiles, other reptiles, 35% of plants

• astroid hit earth? Evidence in iridium concentration (in meteorites)
• Fungi and ferns dominated after; amphibian, croc, turtles, mammals, insects = little effected

Question 9

End- Permian Extinction

Answer 9

Loss of 52% of all families and 96% of all species

21 of the existing 27 families of reptiles and 6 of 9 amphibian families were wiped out

• possible cause: formation of Pangea, sea level changes fell, ocean water turned anoxic (loss of O2) - messed up ocean currents, volcanic eruption (CO2 released - global warming), astroid set off volcanoes, synergism (Sea level changes, anoxic overturn, rapid climatic change, volcanic activity = “world-went-to-hell” hypothesis)

Question 10

Primates

Answer 10

Apes, Great Apes –opposable thumb (grasping)

Question 11

Apes

Answer 11

large brains, no tail, erect posture

Question 12

Great Ape

Answer 12

• Enlarged ovaries
• Enlarged mammary glands - Flattened fingernails
• 32 teeth
• Prolonged parental care

Question 13

Synapomorphy

Question 14

Chimps & Humans share ____ of base pairs of DNA

Answer 14

95%;

proteins are 98.5% similar

Question 15

anything more closely related to humans than chimps

Answer 15

Hominin (most in Africa)

Question 16

H. floresiensis

Answer 16

Fossil found in 2004 Island of Flores, Indonesia

100,000 – 50,000 years ago

1 meter tall, small brain… probably related to/evolved from: H. erectus

Question 17

Homo heidelbergensis
and descendants

Answer 17

left Africa ~600,000 years ago. Spread into Asia & Europe

H. neanderthalensis may have evolved from a H. heidelbergensis ancestor 300,000 years ago, after dispersing into Europe

Question 18

H. neanderthalensis (Neanderthals)

Answer 18

Neanderthals had stouter, more muscular bodies than modern humans

Perhaps body size and shape are an adaptation to the ice ages?

Question 19

Homo sapiens

Answer 19

Out of Africa 60,000–100,000 years ago

Genetic variation higher in Africa

Question 20

More heterozygosity in Africa (more genetic diversity) — less as you move away from Africa

Question 21

Key points:

Answer 21

1. Until ~1.8 mya, most hominins were in Africa
2. H. erectus and descendants appear in the fossil record in Africa, eastern Europe, China & Java around 1.8 mya
3. Ancestors of Neanderthals left Africa ~600,000 years ago
4. Homo sapiens spread around the globe ~60,000 to 100,000 years ago

Question 22

Moderns humans from Europe and Asia share 1-4% of DNA with Neanderthals

Answer 22

Early modern humans arose in Africa, 60,000 years ago, interbreed with Neanderthals in Middle East or Arabia before spreading into Asia and Europe

Question 23

Denisovans

Answer 23

Found in DNA from Denisona Cave; not human or neanderthal - more closely related to neanderthal

Denisovans split from Neanderthals ~200,000 years ago

Modern humans interbreed with Neanderthals, probably as they left Africa

A subset of modern humans interbred with Denisovans as they migrated to New Guinea & Asia

Question 24

1. Genetic diversity in Africa exceeds genetic diversity everywhere else
2. In non-Africans, 1–8% of many have DNA that comes from other Neanderthals and Denisovans
3. In general, our ancestors seem to have replaced archaic peoples as they spread around the globe, but they hybridized with them as well

Answer 24

4. As all humans have African ancestors, DNA from around the world is a subset of the genetic diversity found in Africa. Within humans, about 85-90% of our genetic diversity is within populations, while 10-15% is a consequence of geographic differentiation (between populations). We are genetically very similar across the globe, and human “races” lack genetic reality, though there is some genetic clustering associated with geography (or 23andme.com and ancestry.com wouldn’t work)
5. This is all new! Who were the Denisovans? Are there other groups distantly related to Neanderthals that we don’t yet know about? What if we obtain a H. erectus genome? What would we learn?