Exam 3 (Material after exam 2).

hominids

• Great Apes

Hominins

• humans

• All hominins are hominids, but not all hominids are hominins

List the morphological innovations seen in hominins

• 7-6 MYA: evidence of bipedalism & elongated hinge limbs

• 3.3 MYA: tool making & specialized stones

• 2-1.8 MYA: increase in brain case size

• 1 MYA: evidence of controlled fire use

What order did innovations occur for humans

1. Social structure (Hominids) then Bipedalism (Hominins)

2. Tool Use (Australopithecines), then larger brain cases (Homo genus), Carnivory (Homo genus)

What was African continent like 8 MYA & how did it change over time?

• Miocene era

• lush forests

• 6 MYA climate change begun to cool planet → dry conditions → shift from forests to woodlands to deserts

who is hte only survivor of the adaptive radiation of hominins that occurred in Africa over the last 4-5/7 million years?

• homo sapiens

Who was “Lucy” and why is she important?

• Australopithecus afarensis mostly complete (40%) fossil

• earliest hominin originally discovered

• Omnivorous diet and semi-arboreal lifestyle

When did our ancestors become carnivores? How did this change their ecology?

• 1.8 MYA (Homo erectus) evidence they caught and ate animals

• Carnivores have to roam more broadly to find food- H. erectus dispersed away to hunt

• example of ecological opportunity

Out-of-Africa Hypothesis

• Homo sapiens evolved in Africa and moved into Europe& Asia in a 2nd dispersal event

• Homo erectus populations did not contribute genes to H. sapiens during the secondary contact

What are the alternative hypotheses for the origin of humans

What pattern of diversity would you expect to see to support the Out-of -Africa hypothesis?

• diversity greatest in Africa and decrease outward

• B/c of Founder effect

• oldest originated in Africa, then spread to Europe & outward

How did neanderthal DNA change over time and what does that suggest?

• % Neanderthal DNA in modern humans decreased over time in Eurasia

• Decreased because natural selection against Neanderthal DNA is likely responsible for the change, but some will likely persist!

4. Limited variation passed from Homo neanderthalensis to Eurasian populations of Homo sapiens as a result of admixture that probably took place in Eurasia at some point within the past 100,000 yrs

Did other groups similarily interbreed with Homo sapiens?

• yes, the Denisovans!

How is game theory related to reproductive success?

• Individuals seek to maximize reproductive success so they compete

• predicting how individuals respond to the competition is based on game theory

Hawk-Dove Game Theory

• when hawks are common, doves are more successful

• when doves are common, hawks are more successful

• net result is best strategy that is less equilibrium= Nash equilibirum

Bourgeois Strategy

• flexible behavior in Hawk-Dove games

• behaves like a hawk when defending a resource and a dove when cheating

• includes flexible individuals that’re the most fit

Conspecific (heterospecific) interactions

Altruism

• behavior that increases anothers evolutionary fitness while decreasing the actors own

Why do organisms behave in a way that lowered their own fitness?

• reciprocity- “tit for tat”

• Kin selection & Hamilton’s Rule

• GRoup/Multilevel Selection

• Greenbeard Hypothesis

Kin Selection& Hamilton’s Rule

• organism favors reproductive success of genetic relatives, even at cost of survival/reproduction

• Mathematically explained by Hamilton’s rule as altruist behavior

Group/Multilevel selection

• natural selection operates simultaneously @multiple levels of bio hierarchy

• ex: at genes, cells, organisms, and groups

Greenbeard Hypothesis

• Gene selection

• never demonstrated but see “Medea” gene

• how genes for altruistic behavior can evolve

b

What are the consequences of the price equation?

• evolution of behavior requires communication-prisoners dilemma

• elegance of price equation is in being able to explain all strategies-”honest” signals, cheating and Bourgeois strategy, altruism

Eusociality

• highest level

• overlapping generations

• cooperative brood care

• strict reproductive division of labor

When would eusociality develop?

• ecological contribution-high competition for space & care

• Kinselection-inbreeding:haplodiploid systems

• Delayed Benefits: greater fitness by occupying natal nest

• Multi-level selection: colony as reproductive unit instead of individual

Biological Species Concept

• population can interbreed & produce viable offspring

Evolutionary species concept

• population that shares a pattern of ancestry and descent that represents a single branch of a phylogenetic tree

Phenetic species concept

• population that shares similar traits

Why does it matter to define species?

• B/c of politics

• species can interbreed when mature

Reproductive Isolation

• means to an end

• no longer interbreed and produce viable offspring, thus separate forms

Types of Reproductive Isolation

1. Prezygotic- barriers prevent zygote from forming; ex: mechanical, behavioral, geographic, temporal

2. Postzygotic-barriers reduce fitness of hybrid

How can assortative mating affect populations?

cause populations to diverge

What are the types of Post-zygotic genetic barriers

• Bateson-Dobzhansky-Muller Incompatibilities (BDMIs)-mutations develop in each population that are only maladaptive when they become recombined in hybrids

• Ploidy Changes

• Chromosomal inversions & Translocations- Haldanes rule

Do BDMIs usually occur in hybrids or parental lineages more?

• Hybrids

Haldane’s rule

• heterogametic sex is the one most likely to be afflicted

What are the speciation Models

1. Allopatric

2. Parapatric

3. Sympatric

Allopatric Speciation

• populations diverge because geographic barriers prevent gene flow

Parapatric Speciation

• populations diverge because of a gradient of selection

Sympatric Speciation

• populations diverge despite absence of a geographic barrier

What are the changes in Hybrid Zone over time

Timeline of Speciation

• gradual speciation suggests that populations acquire differences slowly, ex: whales

• punctuated speciation suggests populations diverge rapidly, cannot observe many transitions in form, ex: bats

• Both are likely true!

Abiogenesis

• natural process by which life arises from non-living matter

How does abiogenesis occur?

1. Non-living synthesis of simple organic molecules

2. Polymerization-assembly of simple organic molecules into more complex polymers

3. Formation of self-replicating polymers

4. Compartmentalization of molecules within membranes

5. emergence of protocells with basic metabolic functions