Lect 10: Macroevolution and Speciation

behavior

a phenotypic trait that is shaped by natural selection in an attempt to increase fitness and adaptation of a population

2 types of tempos — gradual change (slow)

evolution occurs through the slow, steady accumulation of small changes over vast periods of time

— whales, horses, tetrapods

2 types of tempos — punctuated equilibrium (fast)

evolution occurs through spurts of rapid change, followed by long periods of stability

— peppered moth, trilobites, mollusks in turkana basin

life

a physical state characterized by the ability to replicate and the presence of metabolic activity

origins of life

possible evidence of how life on earth was formed through the scientific method/thinking

— “warm little pond,” urey-miller experiment

origins of life (phase 1)

the formation of small molecules containing carbon and hydrogen (glucose, etc)

origins of life (phase 2)

the formation of self-replicating, information-containing molecules (dna and rna)

origins of life (phase 3)

the development of a membrane, enabling metabolism and creating the first cells

biological species concept

natural populations of organisms that interbreed with each other or could possibly interbreed, cannot interbreed with organisms outside their own group (reproductive isolation)

speciation

the process by which one species splits into two distinct species

speciation two phases

1. reproductive isolation

2. genetic divergence

reproductive isolation

two populations become separated from one another, leading to two independent evolutionary fates

two barriers to reproduction — prezygotic

individuals are physically unable to mate with each other

OR

if they can mate, the male’s reproductive cell is unable to fertilize the female’s cell

two barriers to reproduction — postzygotic

matings produce hybrid individuals that do not survive long after fertilization

OR

if hybrid offspring survive (like mules), they are intertile/have reduced fertility

genetic divergence

two populations evolving separately accumulate physical and behavior differences over time

allopatric speciation

speciation that occurs as a result of a geographic barrier

sympatric speciation

speciation that occurs within the same geographic area

adaptive radiation

the rapid diversification of a small number of species into a much larger number of species

— share a recent common ancestor

— able to live in a wide variety of habitats

3 triggers of adaptive radiation

1. mass extinctions (sudden and large elimination of species)

2. colonization events (dispersal to a new environment)

3. evolutionary innovations (novel phenotype to exploit its environment in a new way)