Evolution

Archaebacteria were first life forms

Bacteria that could conduct photosynthesis and produce their own sugars survived after life moved to the surface

Increased oxygen → formation of ozone layer → protection from UV radiation → complex life forms thrive

Multicellular organisms start to form (fish → insects → reptiles → first mammals → humans)

Variations within a species

The changes are due to the structural, functional and physiological differences between organisms in a species

Created over multiple generations due to random genetic mutations

The environment influences whether the variation is positive or negative towards an organism

Adaptation and Survival

Changes caused by genetic mutations that have formed over multiple generations

Helps an organism to survive and reproduce while passing on their adaptations

Survival Advantages

Organisms have better chance of surviving due to structural, behavioral or physiological adaptations

Example: Mimicry

Harmless species (viceroy butterfly) adapt to resemble harmful species (monarch butterfly) in order to survive

The process of change in characteristics of a population over multiple generations

Selective Pressure

External environmental factors that can be for or against certain characteristics

Artificial Selection

Selective pressure used by humans in order to create species with desirable and modified traits

Form of biotechnology

Descent with Modification

The process in which species change over time while sharing a common ancestor

Charles Lyell

Uniformitarianism

Slow subtle processes → long term changes

Doesn't include varying geographical activities (natural disasters, climate change, etc.)

Georges Cuvier

Catastrophism

Species are found in certain rock layers; new species appear and disappear over time

Natural events killed species in a specific region → neighboring species repopulate → change

Doesn't include slow processes that cause change in populations

Jean Baptiste-Lamarck

Inheritance of Acquired Traits

Species became more complex over time, causing them to reach a level of perfection

Traits acquired during an organism's life will be passed down to offspring

Doesn't include how we inherit traits

Thomas Malthus

Malthusian theory of Population

Human pops. grow exponentially while food pops. grow linearly → not enough food sources

Sudden event occurs → survival of the fittest → can lead to new species

Stephen Jay Gould & Niles Eldridge

Punctuated Equilibrium

Evolution happens gradually and in small, sudden events

Balance between stasis and punctuated events

Charles Darwim

Natural Selection

Variations (caused by mutations) exist within a species

Survival of the fittest = selective pressure

Organisms with better traits will survive and reproduce

Descent with modification

Stabilizing, directional, and disruptive selection

Stabilizing Selection

For average phenotypes, against extreme phenotypes

Genetic variance in a pop. decreases

Directional Selection

For one extreme phenotype, against other phenotypes

Genetic variance shifts due to exposure of environmental change

Disruptive Selection

For 2 extreme phenotypes. against average phenotype

Fossil Records

Fossils in layers of rock closer to the surface are newer species compared to fossils in deeper rock layers

Fossils appear chronologically

Evolution occurs over time

Anatomy

Homologous structures

Similar structural elements and origins, different functions

Different functions but same set of bones and same organization of bones because of common ancestry

Vestigial Structures

Lost their function but are still apart of the body because of a common ancestor

Biogeography

Study of how organisms have been distributed throughout the world

Organisms on islands are similar to those on the nearest continent

Embryology

Study of early pre-birth stages of an organism

Used to determine relationships between organisms

DNA

Blueprint of the organism

The comparing of DNA allows scientists to determine how closely related two organisms are

2 different organisms with similar genetic pattern = common ancestor

The change in allele frequency in a population

Mutations

Changes that occur in the DNA of an individual organism

Able to change the entire gene flow

Introduce new alleles → changes allele frequency

Gene flow

Total movement of alleles from one pop. to another

Can change allele frequencies in either/both pops.

Genetic drift

Chance events in a pop. → change in allele frequencies

Sample size can have a big impact on the gene pool of a pop.

Two types: Founder Effect & Bottleneck Effect

Founder Effect

Individual organisms (founders) start a new pop. → change in gene pool

Founders carry some alelles from original pop.

Diversity = limited

Occurs often on islands

Bottleneck effect

Fast decrease in pop. → changes in gene distribution

Survivors only have part of original pop. alleles →no gene pool diversity

Non-random mating

Mating on the basis of mate selection for a specific phenotype or inbreeding

The proportion of homozygous individuals in a pop. ↑

Contrast to random mating where breeding partners are random

Likelihood of genotypes mating is based on allele frequencies

Inbreeding is when closely related organisms breed together

Share similar genotypes so frequency of homozygous genotypes ↑

Recessive alleles are expressed more when homozygous genotypes become common

2 types of reproductive isolating mechanisms

Pre-Zygotic

Behavioral isolation: 2 pops. don't respond to each others mating rituals and don't exchange alleles

Temporal isolation: 2 pops. don't exchange alleles because they have specific times to do so during the day or year

Habitat isolation: 2 pops. are in different geographical places and cannot exchange alleles

Mechanical isolation: 2 pops. don't exchange alleles because they're anatomically incompatible

Gametic isolation: 2 pops. exchange sperm + egg but rarely form a zygote

Post-Zygotic

Hybrid inviability: Zygote is created but fails to fully develop due to genetic incompatibility

Hybrid sterility: hybrid is healthy but cannot reproduce

Hybrid breakdown: first gen. hybrids = fertile, offspring of next gen. = fertile, weak

Development of a new species through a variety of factors

Depends on gen. time, environmental conditions, etc

A change in 1 gene or set of genes → isolation

3 types; Allopatric, Parapatric and Sympatric

Allopatric: gene flow is interrupted when a pop. is divided into geographically isolated subpops.

Parapatric: part of a pop. enters a new habitat that borders the parent species (some gene flow may occur in border zone)

Sympatric: happens in pops. that live in the same geographic area

Less common than allopatric

Happens when gene flow is diminished by sexual selection, polyploidy and/or habitat differentiation