Exam #2 key terms

Module 5:  Natural Selection

Rule of Life:  Natural Selection is the only Well-Corroborated Explanation for the Evolution of Adaptive Traits

How Darwin Discovered Natural Selection (see video)

Prior thinkers:  Lamarck, Lyell

Influence of understanding of Artificial Selection

Influence of Malthus

A. What natural selection is

Lamarck’s explanation for adaptive evolutionary change, and evidence against Lamarck’s explanation

Darwin’s explanation for (apparent) intelligent design

How did Darwin find evidence of gradations of complexity in evolution of complex traits?

What are the core components of natural selection (there are three)

The importance of thinking in terms of POPULATIONS

Measuring and representing VARIATION

Evidence for INHERITANCE

Pattern of inheritance for “Mendelian” traits

Pattern of inheritance for “Polygenic” traits

Measuring polygenic inheritance:  “Heritability”

Definition of DIFFERENTIAL SUCCESS and relationship to phenotypic variability

Artificial Selection

How it differs from Natural Selection

How Darwin used it to explore his ideas

Examples

Natural Selection

Differential success with a Mendelian trait:  Sickle Cell

Why is a deleterious mutation (Sickle Cell mutation) maintained by natural selection in some human populations?

Differential success with a polygenic trait—relationship to Heritability of trait

Sources of phenotypic and genotypic variation in natural populations

Other agents of evolutionary change besides natural selection

Agents of (natural selection) in natural populations (biotic and abiotic factors)

Modes of Selection:  Directional, Stabilizing, and Disruptive

Summary of Darwin’s hypothesis:  how does it differ from Lamarck’s

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Supplementary Module: AVIDA
Introduction to Boolean logic (And, Not, XOR, etc)

Avida:  platform for studying evolution experimentally in computer system

Components:

Population of self-replicating computer programs (Avidians)

Each Avidian has genome consisting of list of computer instructions, and capacity to replicate

Replication happens with small probability of mutation

Reproductive success depends upon how efficiently avidians solve problems set by experimenter

Thus Avida has Variation, Heritability, Differential success, making it an instance (not just a simulation) of Darwinian selection

Avida instructions in the right sequence can compute wide variety of functions

Whether avidians compute the RIGHT function depends upon evolution

How this can be used to study evolutionary dynamics  experimentally

What the effect of mutation rate is

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B. EVIDENCE that traits are shaped by natural selection

Inferences from the OUTCOMES of natural selection

Problem-oriented vs Trait-oriented approaches (refers to ways of framing questions)

Comparative vs. Experimental methods for providing evidence

Divergent evolution of homologous trait correlated with evolved function in different environments

Convergent evolution (independent evolution of similar trait from different starting points)

Example:  Adaptations of cacti for survival in deserts

Example:  Testing function of cactus spines (experimental and comparative evidence)

Example:  Testing function of CAM photosynthesis (comparative evidence)

Example:  Adaptations of vertebrates to swimming (comparative:  divergent and convergent outcomes)

Example:  Evolution of “endothermy” (warm-bloodedness) in fish (comparative evidence)

Inferences from the direct study of natural selection AS IT HAPPENS

Galapagos Finches

Evidence for how different finch species are related

Pattern of beak evolution over time in the medium ground finch, Geospiza fortis

Evidence that beak evolution is caused by natural selection

Other approaches:  artificial selection, experimental evolution, digital evolution

C.  Limits on Natural Selection

Irreducible complexity:

As a critique of Darwin’s theory

How irreducibly complex traits could evolve in a step-by-step process

Examples

Module 6:  Sexual Selection

Rule of Life:  Sexual Reproduction is a Consequence of Evolution by Natural Selection, and Also Has Profound Consequences for Shaping the Course of Evolution

Basic questions about sex

Define sexual vs asexual reproduction (with examples of each?)

Why reproduce sexually (which implies consideration of the COSTS of sex)?

What explains why sex ratio (#males:#females) is so often 1:1? (consider payoffs of producing male vs female offspring depending upon what rest of population is doing)

Why are sexes so different?

Explaining evolution of sex differences

Secondary sexual characteristics (define and give examples)

Why such traits were puzzling to Darwin

Key drivers of evolution of sex differences

Anisogamy:  what is it and why does it matter for selection pressures operating on males and females?

Operational sex ratio: what is it, why does it vary, and why does it matter for selection pressures operating on males and females?

What are fundamental limits on potential reproductive success (RS) of females vs males?

Bateman’s principle

Sexual selection: define it and compare it to natural selection

Two forms of sexual selection (intrasexual and intersexual selection)

      Identify and describe

      Give examples of traits that evolve under each of these

      Understand how “sperm competition” is a form of intrasexual selection—and what traits arise from this mode of competition

Why are females so often more choosy about their mates than are males?

What are criteria for female choices? (resources vs good genes)

Evidence for choice based on good genes

Example:  choice by female bower birds

Example:  Choice based on odor to detect whether mate is good partner relative to the MHC allelic diversity

Mating systems and parental care

What are characteristics of different mating systems?

Why is monogamy most common in birds, and polygyny most common in mammals

Why would supposedly monogamous female birds engage in extrapair copulations and why would they keep them secret?

Under what circumstances would males evolve a tendency to be choosy about whom they mate with?        

Module 7  Origin and Extinction of Species

Rule of Life: New species are formed when populations of an ancestral species get separated, diverge in isolation under natural selection, and evolve to eliminate gene flow between them

Rule of life: Species can go extinct for selective or non-selective reasons, and once extinct can never reappear

Understand “species” as a collection of organisms that share things in common

Morphological species concept:  collection of organisms that look alike (in spite of variation among individuals, among populations, or over time)

Ways in which morphological species concept is reliable [REVISIT IDEA OF HOMOLOGY]

Importance of morphological species concept for fossil record

List of “problems” with morphological species (observations that call this concept into question)

Biological Species Concept (developed by Ernst Mayr)

What is it?

What is role of sexual reproduction in defining it?

Why it leads to the view of species as the “unit of evolution”

Why it helps explain discontinuities among species (lack of smooth gradations in phenotype)

What the Geographic Speciation Hypothesis describes:

Geographic Isolation

Separate and divergent evolution

Reunification

Selection against hybrids

Reproductive isolation

What are causes of geographic isolation?

Predictions of this hypothesis

            That there has ample opportunity and time

            Recently diverged species should be near each other

            Geographic speciation still underway

            Reproductive isolation increases with time since geographical isolation

            Hybrids should be infertile or otherwise disfavored by sexual selection

Case studies

Snapping shrimp on either side of the isthmus of Pamama

Galápagos finches

Host races of Apple maggot fly

What does the case of the “quagga” illustrate? (unreliability of morphological species concept; existence of geographical “races”)

What are causes of selection against hybrids?

Post-zygotic (natural selection

Pre-zygotic (role of mate choice and sexual selection)

Hybrids may form even millions of years after species diverged (genus Equus)

New material on extinction

All species have possibility of going extinct, and once extinct will never reappear

What causes extinction?

"Background" extinction

Rate of appearance of new species may balance or surpass rate of extinction

Average "lifespan" of species can be determined based on appearance and disappearance from fossil record

    For vertebrates as a group the average species lifespan is about 1 million years (with a lot of variation around this average)

"Background extinction rate" can be estimated from average species lifepan

Background extinction affects species, but generally not higher level taxonomic groups (genera, families, orders, classes, etc)

Mass extinctions

There have been five truly massive extinctions in the past 600 million years

Rate of extinction FAR exceeds rate of origin of new species, leading to loss of biodiversity

Extinction affects higher taxonomic levels:  whole genera, families, or orders may go extinct

Example: Dinosaurs

Evidence that a sixth mass extinction has begun?