Cal Poly BIO 263 Midterm 1 Lema

Evolution

Descent with modification, or change in the genetic composition, form and/or behavior of organisms over generations.

Two major contributors to evolution

Charles Darwin and Alfred Russel Wallace

2 major themes of biological evolution

Process (Natural selection, genetic drift, etc.) and history (what has evolved)

Age of Earth (Creationist perspective)

6000 years

Creationist view of species

do not change, created independently

Plato view of species

Species are unchanging types, variations unimportant, even misleading

Essentialism

Essential qualities or characteristics of things

Typological thinking

Putting things into categories based on characteristics

Great Chain of Being

Aristole, Scala Naturae, Fixed sequence based on increasing size and complexity, humans at top

1700s popular thinking

1. Species are fixed types

2. Some are higher- more complex or "better'

What changed the Pre-Evolutionary world view?

1. Challenges to the account of human history

2. Challenges to origin of the earth (geology, fossils, etc.)

Ussher

Calculated age of the earth based on Hebrew Patriarchs

Charles Lyell

Popularized James Hutton's concept of uniformitarianism

Uniformitarianism

that the Earth was shaped by gradual processes that are still active today

Charles Lyell's view of Species

Extinction yes, evolution no

Lamarck's Theory of Evolution

1. Organisms originated by spontaneous generation, evolve by moving up

2. Inheritance of acquired of characters. Change in response to environment passed on to offspring.

Assumptions of Lamarck's Theory

-Lower organisms show up

-To have evolution, things evolve from lower organisms to higher organisms

-Changing yourself can change offspring (sort of epigenetics)

Lamarck's view of Species

Species change through time

-Multiple origins of life

-No extinction (1809 before extinction became popular)

Buffon's Law

despite similar environments, different areas of the globe have different animals

Four Postulates of Natural Selection

1. Variation

2. Inheritance

3. Tendency towards population growth

4. Differential survival and reproductive success

Adaptation

heritable trait that increases fitness of an individual with that trait, compared to individuals without that trait, in a particular environment

Unit of natural selection

phenotype of individuals

Unit of evolution

population

Important points of natural selection

1. Mutation is random

2. Variability exists but heritable variability is only acted on by natural selection

3. New heritable traits results from mutations

Normal Curve

Bell-shaped distribution pattern

Narrow normal Curve

low variation

Wide normal Curve

high variation

Directional Selection

Change in average in a certain direction

Mechanisms of Evolution

1. Natural Selection

2. Genetic Drift

3. Sexual Selection

Stabilize Selection

Maintains intermediates phenotypes, reduces variation

Disruptive Selection

Intermediates selected against, maintains or increases variation, does not change mean and may lead to speciation

Hardy-Weinberg Principle holds true under...

1. Random mating

2. No natural selection

3. No genetic drift

4. No gene flow

5. No mutations

Genetic Drift

Allele frequencies drift randomly over time not adaptively

-Eventually leads to random loss or fixation of alleles

-especially pronounced in small populations

Founder Event

Group starts new population in new area

Founder effect

Allele frequencies differ from the original population

Genetic Bottleneck

Population becomes very small, and sudden reduction in alleles

Gene Flow

Movement of alleles between populations; individuals leave a population; join another and breed.

Sexual Selection

Animals evolved extravagant characteristics, colors and displays to better obtain mates and increase reproductive success (traits aren't always adaptive in the context of natural selection)

Parental Investment

Whatever parent does to increase survival of existing offspring at the cost of the parent's ability to generate more offspring.

Limiting Factors for sexual selection for females

-Her ability to produce eggs

-Ability to provide parental investment

Limiting factors for sexual selection for males

-Ability to secure mates

-Competition with other males

-Females by choice

Species

An evolutionary independent population or group of populations

3 Approaches to identify species

1. Biological Species Concept

2. Morphological Species Concept

3. Phylogenetic Species Concept

Creator of Biological Species Concept

Ernst Mayr

Biological Species Concept

Species are defined based on reproductive isolation (cannot interbreed or fail to produce viable offspring)

Disadvantages of Biological species concept

-Cannot be evaluated in fossils it in species that reproduce asexually

-Can only be applied to populations that overlap geographically

Prezygotic Isolation

Occurs when there is a barrier to stop mating

Types of Prezygotic Isolation

1. Temporal- breed at different times of a year

2. Habitat (physical isolation)

3. Behavioral

4. Gametic (sperm and egg are not compatible)

5. Mechanical (parts don't fit)

Postzygotic Isolation

Produce hybrid with low fitness, hybrid in-viability, or hybrid is sterile

Morphospecies Concept

Species are identified be difference in morphological features (traits arise from isolation)

Disadvantages of morphospecies concept

-cannot identify a cryptic species

-features used to distinguish are subjective

Phylogenetic Species Concept

Defined by cladistic monophyly

Speciation

Splitting of populations of a single species due to genetic isolation

Allopatric Speciation

Speciation caused by physical isolation and genetic isolation

Dispersal

Mode of allopatric speciation- colonizes new habitat forms new population

Vicariance

mode of allopatric speciation- physical barrier, isolated subgroups

Sympatric Speciation

Speciation in same geographic area

Polypoidy speciation

Type of sympatric speciation- where gametes don't split chromosomes correctly, common in plants

Polytomy

More than one branch from one mode

Homology

Similarity due to a shared ancestor

Homoplasy

similarity be convergent evolution

Synapomorphy

Shared derived character state

Symplesiomorphy

shared primitive character state

Apomorphy

uniquely derived characters that are specific to just one taxon

Monphyletic group

All organisms on a branch of phylogenetic tree descended from a single common ancestor