Lecture 10: Macroevolution & Speciation

Origins of Life, Evolution, and Macroevolution

Microevolution

Change in allele frequencies/gene pools over one of a few generations

What are the 4 Mechanisms of Microevolution

1) Mutation

2) Genetic Drift

3) Migration/Gene Flow

4) Natural Selection

What does a change allele frequencies/gene pools lead to?

fitness and adaptation of a population, therefor the population will evolve over generations

Behavior

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

Describe the process by which various environments and behaviors lead to the existence of different kinds of organisms on Earth

Natural selection driving adaptations that increase a population's fitness

Macroevolution

Changes among species over a long period of time

At what level is macroevolution measured? - provide an example

above species level

ex: instead of looking at an individual beetle species, zoom out and look at the entire beetle clade

What is macroevolution an effect of?

macroevolution is an accumulated effect of microevolution over time

What are the 2 types of tempo of evolution?

1) Gradual change (slow)

2) Punctuated equillibrium

What is gradual change? - provide and example

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

Ex: whales, horses, tetrapods

Which microevolutionary mechanism would most likely cause gradual change, and why?

natural selection because it works by consistently favoring advantageous traits over generations

Which mode of natural selection is gradual change measured by, and why? - provide an example

Gradual change is measured by directional selection because as environmental pressures act upon a population, selection pressures can act consistently in one direction, gradually shifting the population’s phenotypic distribution.

Ex: gradual increase in size or change in color

What is punctuated equilibrium? - provide an example

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

Ex: peppered moth - industrial revolution (smog)

which microevolution mechanism most likely cause the tempo of evolution called punctuated equilibrium?

Genetic drift (isolated populations) or Natural Selection (new environments)

Life

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

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

The “warm little pond” and the Urey Miller experiment

What are the 3 phases of how life originated on earth?

Phase 1: the formation of small molecules containing carbon and hydrogen

Phase 2: the formation of self-replicating, information-containing molecules

Phase 3: the development of a membrane, enabling metabolism and creating the first cells

What is the biological species concept?

The natural populations of organisms that

• interbreed with each other or could possibly interbreed

• practice reproductive isolation: cannot interbreed with organisms outside their own group

Species vs Not a species

species: plants, animal, all humans

not a species: hybrids

• reproductive isolation, sterility, human intervention

Speciation

the process by which one species splits into two distinct species

What are the 2 phases in which speciation occurs?

1) reproductive isolation

2) genetic divergence

Define reproductive isolation and the types of barriers to reproduction.

reproduction isolation: two populations become separated from one another

2 types:

• pre-zygotic: when individuals are physically unable to mate with each other or if individuals are able to mate, the males reproductive cell is unable to fertilize the female reproductive cell

• post-zygotic: when matings produce hybrid individuals that do no survive long after fertilization or if the hybrid offspring survives (such as a mule), hey are infertile or have reduced fertility

Define genetic divergence. How does it happen?

two populations evolving separately accumulate physical and behavior differences over time

• through mutations, natural selection, and genetic drift

What are the 2 types of genetic divergence speciation?

1) allopatric speciation

2) sympatric speciation.

Define both types of genetic divergence speciation

1) allopatric speciation: speciation that occurs as a result of a geographic barrier

2) sympatric speciation: speciation that occurs within the same geographic area

Define Adaptive radiation and provide an example

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

Ex: Darwin finches in Galapagos islands

Identify and define the 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 it’s environment in a new way