Evolutionary Biology Unit 1

University of Arkansas

Evolution

Any heritable change in a population over time.

What do mechanisms do?

Responsible for the generation of heritable variation.

The sorting of heritable varaiton.

Examples of mechanisms?

Mutation and Migration.

Mutation is the main way.

Examples of sorting heritable?

Selection (Natural & Sexual) & Random genetic drift

Selection

Non-random sorting of variants based on differences in the ability to survive and reproduce.

Fitness

The ability to survive and reproduce.

What is random genetic drift?

Random sorting process that occurs in a finite population due to chance effects.

Examples of random genetic drift?

Bottleneck and sampling errors during reproduction.

Science defintion

A body of knowledge about the natural world and the process of generating it by observation and experimenting. Evidence-based

Scientific Ideas

Must have the ability to be falsifiable.

Hypothesis

A statement of what might be true

Fact

A hypothesis so firmly supported by evidence that scientists assume it is true.

Theory

A mature, coherent body of interconnected statements or hypotheses, based on reasoning and evidence

Fact of evolution

Change over time

Theory of evolution

Hypotheses that explain how evolution works.

Mechanisms of evolution.

Misconception: “Evolution is just a theory”

It’s not a specualtion, but supported by evidence.

Not just a theory, it’s also a fact.

Misconception: “Evolution is natural selection”

It’s an oversimplification

Natural selection is just one of the mechanisms of evolution.

Misconception": “Evolution is entirely random”

Selection is a non-random sorting process.

Where differential fitness of variants determines the direction of evolution.

Misconception: “Evolution violates the 2nd law of thermodynamics”

The Earth is not an isolated system because the sun provides constant energy.

Misconception: “Evolution is a march of progress”

Evolution lacks foresight.

Evolution is not a ladder-like progress, but a branching process.

We do not come from chimps, we share a common ancestor.

Misconception: “Evolution always proceeds from simple to complex.”

Simplification can occur.

Theory of Organic Progression

From Lamarck,

Species first originate by spontaneous generation and evolve up the scale of organization from simple to complex forms of life. Leading to the pattern of the Great Chain of Being.

Transformational Theory

From, Lamarck

New heritable characteristics can be acquired through the effect of use or the environment.

The 2 major characteristics of the theory of organic progression

No extinction & no common ancestor between different species

Unit of Evolution in Transformational theory

The individuals.

Key idea/assumption of transformational theory

Acquired somatic (body) cell traits are inheritable.

Examples: Ability to have tanner skin & the building of muscle.

Theory of descent with modification from a common ancestor

From Darwin,

Fact of Evolution. Viewed biodiversity as the product of biodiversification as the product from common ancestors.

Characteristics of theory of descent with modification from a common ancestor

Extinction common

Shared ancestry between

Theory of Natural Selection (Variational/population theory of evolution by natural selection)

The frequency of genetically distinct variance in a population changes over time due to differential fitness.

What is the unit of evolution in the theory of natural selection?

The population.

What is the unit of selection in the theory of natural selection?

The individual.

What is the key distinction between variational theory and transformational theory?

Individuals do not evolve, the population evolves.

The 3 conditions for natural selection to occur are?

Variation, heritability, & differential fitness

What are the two major components that make up total phenotypic traits?

Genetic variance & environmental variance

V_p= V_G + V_E

Formula for heritability

h²=(V_G)/(V_P)

What is the range for heritability? (h²)

It ranges from 0 to 1.

What does it mean when h²=1?

Total phenotypic variance equals genetic variance. 100% of variance is explained by genetic variance

V_p=V_G

What does it mean when h²=0?

Total phenotypic variance equals environmental variance. 100% of variance is explained by the environment.

V_p=V_E

What does h² equal to in a graph?

The sloped of a parent-offspring regression line.

What is the equation for intra-generational change?

S = X_B - X_P

What is the equation for inter-generational change?

R = X_OS - X_P

What is the equation for heritability using intra & inter generational change?

h²= R / S

The Breeder’s equation is

R= (h²)(S)

When h² = 0, what is R?

R=0, there is no evolution occuring.

When h²=1, what is R?

R=S, they can be used to predict offspring values.

Truncation Slection

A form of directional selectional.