College Bio 2 Unit 1

Macroevolution

Macroevolution

Evolutionary changes the create new species

Microevolution

Evolution as it relates to allele frequencies

Drawbacks of Morphological Traits

How many traits to consider, traits my very continuously, what degree of dissimilarity, members of the same species can look different, members of different species can look similar

Biological Species Concept

Group of individuals whose members have the potential to interbreed with one another and produce fertile offspring

Evolutionary Lineage Concept

New species are the result of speciation from immediate ancestral species - Individual

ecological species concept

Each species occupy an ecological niche with a unique set of habitat resources, species also influences ecosystem

General Species Concept

Each species is a population of individually evolving lineages

Phylogenetic Species Concept

Monophyletic groups identified by synapomorphies

Morpholocal Species Concept

Evolutionary independent lineages vary by size, shape, and other features

Reproductive isolation

Mechanism that prevents interbreeding between species

Interspecies hybrid

When species produce hybrid

Prezygotic isolation

Mechanism that prevents the formation of a zygote. Includes: Habitat: Different habitats Temporal: different breeding times Behavioral: different species have different mating rituals Mechanical: reproductive organs don't fit Gamete: the sperm is unable to fertilize the eggs

Postzygotic isolation

After the zygote has formed Hybrid Inviability: Prevents the offspring from reaching a reproductive age Hybrid sterility: Offspring can't reproduce Hybrid breakdown: subsequent generations become weaker until line dies out

2 explanations for speciation

1. abrupt events that cause chromosome number to change

2. consequence of adaptation to different ecological niches

Allopatric speciation

Members of a species become geographically separated Dispersal: the species move Vicariance: event splits population

sympatric speciation

Occurs when members of a species that are within the same range diverge into 2+ species with no physical barriers

mechanisms of sympatric speciation

Polyploidy, adaption to local environment, sexual selection

Taxonomy

Science of describing, naming, and classifying living/extinct organisms

Systematics

the study of biodiversity and the evolutionary relationships among organisms

Binomial Nomenclature

Latin names - Genus species (italicize) Established by international organizations

Phylogeny

Evolutionary history of a species or group of species.

Anagenesis

Single species evolves into a different species over time

Cladogenesis

single species diverges into 2+ species

Clades

Group of species (taxon) consisting of an ancestor and descendants

Monophyletic Group:

group that consists of a single ancestral species and all its descendants; includes individual clades

Paraphyletic

Not all descendants are included in the grouping

Polyphyletic

Specific traits evolve separately in different species (homoplasies /convergent evolution)

Synapomorphy

Trait found in 2+ taxa that are present in recent common ancestors but missing in more distant ones

Shared Primitive Character

Shared by 2+ taxa and is inherited from an ancestor older than the last known common ancestor

Shared Derived Character

Shared by 2+ taxa, originated from the most common ancestor

Outgroup

The most primitive ancestor, diverged before the rest of the species

Parsimony

Simplest way to organize characters and states

Neutral Theory of Evolution

Favorable mutations are rare, detrimental mutations are quickly eliminated, neutral mutations occur at a constant rate

Horizontal Gene Transfer

Any process in which an organism incorporates genetic material from another organism without producing offspring

Vertical Gene Transfer

Sexual reproduction, changes in groups due to descent from common ancestor

Habitat Bias

Fossils are only found in areas where sediment is distributed

Tissue Bias

Hard-bodied organisms are more likely to be preserved

Temporal Bias

Recent organisms are more common than ancient fossils

Abundance Bias

Common, widespread, long lasting species are more likely to be fossilized

Life's Timeline

1. Precambrian - unicellular organisms, no oxygen

2. Panerozoic Era - Paleozoic: most lineages Mesozoic: Dinosaurs, gymnosperms Cenozoic: mammals, angiosperms

Gymnosperm

Cone bearing plant

Angiosperm

Flowering plant

Adaptive Radiation

A single lineage produces many descendants with a wide range of adaptive forms

HOX Genes

series of genes that controls the differentiation of cells and tissues in an embryo

What lead to the explosion of life?

• High oxygen levels and aerobic respiration

• Predation, drilling through sea shells

• New niches form on the sea floor

• New genes lead to new bodies

Permian Extinction

• 90% of life disappeared, extensive flood basalts added CO2 to the atmosphere, leading to coal fires

• High levels of SO2 lead to acid rain, oxygen in the ocean disappears and bacteria thrives

Impact Hypothesis

Extinction event caused by an asteroid - left high levels of iridium, shocked quartz, and leaolinite

Evolution

The change of alleles in a population over time

Aristotle

Life is perfect, there are no changes or variations - Scala naturae

George Buffon

Proposed that living things change through time

Catastrophism

Each boundary between strata correspond to a catastrophe

Hutton/Levy

Geologists, studied the rocks in the grand canyon, proposed that Earth's forces pushed the rock layers upward

Uniformitarianism

Processes stay the same over the course of Earth's history

John Baptiste Lamarck

Theory of acquired traits, heritable experience

Thomas Malthus

Economist, humans are born faster than they are dying, leading to overpopulation

Alfred Wallace

Darwin's mentor, came up with the theory of evolution by natural selection using biogeography

Charles Darwin

• All organisms are descended from an ancestral species, proposed descent with modification (Galapagos tortoises, finches)

• Tested via artificial selection with pigeons

• Species diverge from common ancestor

Evidence of Evolution: Fossils

• Fossil record, show history of life and how different groups of organisms change over time

• When animals die, tissue decays, and hard parts are replaced with silica/pyrites

Evidence of Evolution: Relative/Absolute Dating

Relative= based on sediment layers Absolute = carbon dating (percentage of N14 compared to C14, as is broken down through beta decay)

Transitional Forms

Intermediate states between ancestral and current forms Ex: Fishapods, or Tiktaalik, explains land vertebrate, missing link between aquatic and land organisms

Evidence of Evolution: Biogeography

Species with a common ancestor are found in different geographic locations

Convergent Evolution

2 species with different lineages develop similar characteristics

Analogous Structures

Similar adaptive characteristics - species from different linages develop similar traits due to a shared environment Ex: birds and bats

Artificial Selection

Reduces genetic variation, can be harmful to species Ex: bulldogs

Homologous Structures

Similar structures with different functions Ex: a human hand v the flippers of marine mammals

Vestigial Structures

Have no apparent function in one species, is homologous in another Ex: hip bone in whales

Embryonic Development

More closely related species have similar embryonic development

Genetic Homology

Similarities in DNA sequences or amino acid sequences that are due to inheritance from a common ancestor.

Developmental Homology

seen in embryos of different species

Divergent Evolution:

Traits held by common ancestor evolves into different variations over time

Coevolution

Close interacting species exert selective pressures on one another, and they evolve together Ex: flowers and bees

Gene Pool

All of the alleles for every gene in a given population

Polymorphism

Presence of 2+ variants or traits for a given character

Hardy Weinberg Equation

p2 + 2pq + q2 = 1 p + q = 1

4 Mechanisms that shift allele frequencies

• Natural Selection: increase in the frequency of alleles that contribute to reproductive success

• Genetic Drift: causes allele frequency to change randomly

• Gene flow: occurs when individuals leave a population and join another

• Mutation: modifies allele frequencies

Hardy-Weinberg equilibrium

-No mutation -No gene flow -Random mating -Large populations -No natural/sexual selection

Genetic Variation

Relative frequency of alleles present in a particular population

Adaptations

Changes in population of living organisms that increase the ability to reproduce

Two categories of reproductive success

Adaptation - survive to reproductive age Reproductive traits - Traits that help organisms find mates

Fitness

The measure of reproductive success

Directional Selection

Average phenotype changes in one direction - favorable allele will approach a frequency of 1.0. Ends in purifying selection Ex: Cacti with more spines have greater reproductive success

Stabilizing Selection

Average value of a trait doesn't change, reduces extremes, frequencies approach 0.5 Ex: average birth weight of human babies

Disruptive Selection

Favors extreme phenotypes at both ends of the range, increases variation of a trait Ex: black bellied seed crackers develop large or short beaks depending on seed size

Speciation

Product of disruptive selection, formation of new species

Balancing Selection

Maintains variation, balance among alleles, favors heterozygotes Ex: sickle cell anemia

Balanced polymorphism

2+ alleles are kept in balance, maintained in population over the course of a generation

Sexual selection

Form of natural selection directed at certain traits of sexually reproducing species

Intrasexual selection

Occurs between members of the same sex, results in competition for mating opportunities and territory

Intersexual selection

Occurs between opposite members, results in female choice and showy characteristics

Fundamental Asymmetry of Sex

Females invest more in offspring: Female fitness is limited by ability to gain resources Male fitness is limited by number of mates

Bateman-Trivers Theory

When certain alleles increase male attractiveness to females, the frequency of those alleles will increase

Female Choice

Females prefer healthy males - In birds, their brightly colored feathers are the result of carotenoids, which also protect tissue and help to improve the immune system

Sexual dimorphism

any trait that differs between males and females

Genetic Drift

A change in the allele frequency of a population as a result of chance events rather than natural selection, frequency of allele is 0 or 100

Genetic Drift - Bottleneck

population size dramatically decreases for at least 1 generation, then rebuilds, surviving members have different allele frequencies from the original population Ex: the American bison after being hunted to near-extinction

Genetic Drift - Founder Effect

Small group of individuals separate from larger population, form a new colony

Neutral Theory of Evolution

Do not affect phenotype, most genetic variation is due to the accumulation of neutral mutations that have attained high frequency

Nonrandom mating - Assortative Mating

Individuals with similar phenotypes are more likely to mate

Nonrandom mating - disassortative mating

Dissimilar phenotypes mate, resulting in heterozygosity

Mutations

Restore genetic diversity, random with respect to fitness, can change frequency of allele over time