Bio 191 Exam 1 : Chapters 19-23

Evolution

-descent with modification
-all organisms are related through descent from an ancestor that lived in the remote past.

Fossils

-remains or traces of organisms from the past
-usually found in sedimentary rock

Strata

-layers of sedimentary rock

Ancestral

-species are found in lower layers
-don't use primitive

Derived

-species are found in upper layers
-don't use new

Galapagos Islands

-chain of islands near South America where Darwin developed his theory of natural selection by studying the unique life there.

Adaptation

-is a process
-both a verb and a noun

Adaptations

-traits that improve an individual's ability to survive and reproduce
-ex. beaks of the finches

The history of life

-is like a tree with branches
-ancestral species seen earlier
-derived species seen later

Extinct vs. Extant

-extinct, species is no longer in existence
-extant, species are currently in existence

Artificial Selection

-humans have modified other species by selecting and breeding individuals with desired traits.
-ex. dogs derived from wolves

Darwins Two Observations

-members of a population often vary in their inherited traits.
-all species can produce more offspring than their environment can support, and many of these offspring fail to survive and reproduce.

Darwins Two Inferences

-individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals.
-this unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.

Rise of new species

-if an environment changes over time, natural selection may result in adaptation to new conditions and may give rise to new species.

Individuals and Populations

-individuals do not evolve; populations evolve over time.

4 types of data that document the pattern of evolution

-direct observations
-homology
-the fossil record
-biogeography

Direct observations of evolutionary change

-hard to do

Homology

-similarity resulting from common ancestry

Homologous Structures

-are anatomical resemblances that represent variations on a structural theme present in a common ancestor
-allow us to group together
-bone structure is the same because they were inherited from the same place

The fossil record provides evidence of...

-the extinction of species
-the origin of new groups
-changes within a group over time

The fossil record

-
-will never be complete
-can document important transitions (transition from land to sea in the ancestors of cetaceans)

Biogeography

-geographic distribution of species
-the study of past and present distribution of organisms
-knowing where organisms have lived over time

Pangea

-Earths continent was formerly united in a single large continent
-separated by continental drift

Drug-Resistant Bacteria

-strains of a bacterium that have adapted and are no longer controlled or killed by normal antibiotic treatment
-provides example evidence for natural selection

Staphylococcus Aureus (S. aureus)

-commonly found on people's skins or in their nasal passages.
-resistant to penicillin (1945)
-resistant to methicillin (1961)

Methicillin-resistant S. aureus (MRSA)

-an infectious disease caused by a pathogen that is resistant to many antibiotics
-dangerous pathogen

Vestigial Structures

-remnants of features that served important functions in the organism's ancestors.
-evolutionary leftovers
-show our evolutionary history
-helpful for comparative purposes

Homologies at the molecular level

-genes shared among organisms inherited from a common ancestor
-greater difference equates to longer distance in connection.

Convergent Evolution

-the process by which unrelated organisms independently evolve similarities when adapting to similar environments.
-does not provide information about ancestry.
-ex. flying squirrel and sugar glider.

Analogous Evolution

-Structures that are similar but do not have a common evolutionary origin; results from CONVERGENT EVOLUTION (e.g., a bird's wing and a bee's wing: few structural similarities but essentially perform the same function).

Analogous vs Homologous

-analogous features share similar functions, but not common ancestry; homologous features share common ancestry, but not necessarily similar functions.

Darwin's Four Postulates

-Individuals in a population vary in the traits they possess.
-Some trait differences are heritable.
-Survival and reproductive success are variable among individuals in a population.
-Individuals with certain traits are more likely to survive and reproduce.

Phylogeny

-evolutionary history of a species or group of related species.

Systematics

-the science of naming and grouping organisms

Taxonomy

-the scientific study of how living things are classified.
-giving things a name. (two parts)

Taxonomy vs Systematics vs Phylogenetic's

-think of all three as the same thing
Taxonomy: naming and classifying organisms
Systematics: provides scientific names, describes, preserves collections, provides classifications, keys for identification, data on distributions, investigates evolutionary histories and considers environmental adaptation of organisms.
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Taxonomic groups from narrow to broad

species, genus, family, order, class, phylum, kingdom, domain.

"Dear King Philip Came Over For Good Soup"

Binomial

-the two-part scientific name of a species

Genus

-the first part of the name.
-the first letter is capitalized.
-entire two-part name is italicized or underlined

Epithet

-the second part of the name
-unique for each species in the genus

Clade

-an evolutionary branch of a cladogram that includes a single ancestor and all its descendants
-a branch of an evolutionary tree

Node

-point on evolutionary tree

Phylogentic Tree

-evolutionary relationships in branching

Sister taxa

-groups that share an immediate common ancestor

rooted

-includes a branch to represent the last common ancestor of all taxa in the tree

Homology vs Analogy

-homology is similarity due to shared ancestry
-analogy is similarity due to convergent evolution

Homologies

-phenotypic and genetic similarities due to shared ancestry

Homoplasies

-analogous structures or molecular sequences that evolved independently

Cladistics

-classifies organisms based on common ancestry

Clade

-a group of species that includes an ancestral species and all its descendants.

Molecular Clock

-uses constant rates of evolution in some genes to estimate the absolute time of evolutionary change.

HIV

-descended from viruses that infect chimpanzees and other primates
-virus evolved in a very clocklike way

Three domains of life

-bacteria, archaea, eukarya

Domains Bacteria and Archaea

-single-celled prokaryotes

Domain Eukarya

-multicellular organisms
-protists, fungi, plants, animals

Horizontal Gene Transfer

-movement of genes from one genome to another
-occurs by exchange of transposable elements and plasmids, viral infection, and fusion of organisms
-complicates efforts to build a tree of life

Microevolution

-smallest possible scale
-a change in allele frequencies in a population over generations
-population genetics

Genetic Variation

-differences among individuals in the composition of their genes or other DNA segments
-phenotypic variation often reflects genetic variation
-caused by differences in genes or. other DNA sequences

Sources of Genetic Variation

-mutations
-genetic recombination in sexual reproduction
-lateral gene transfer.

Mutations

-a change in the nucleotide sequence
-effects can vary
-almost always they are bad, rarely they are good

Sexual Reproduction

-recombination of alleles
-three mechanisms: crossing over, independent assortment, random fertilization.

Population

-localized group of individuals capable of interbreeding and producing fertile offspring

Gene Pool

-consists of all the alleles for all loci in a population

Hardy-Weinberg Principle

-describes a population that is not evolving
-frequencies of alleles in a population remain constant from generation to generation
-if frequencies of alleles in a population are changing it can be concluded that the population is evolving

Formulas:
p^2+2pq+q^2=1
p+q=1

Conditions for Hardy-Weinberg Equilibrium

1. No mutations
2. Random mating (no sexual selection)
3. No natural selection
4. Extremely large population size
5. No gene flow

-these conditions are rarely met in nature

3 factors that alter allele frequencies

1. Natural Selection
2. Genetic Drift
3. Gene Flow

-break the HW equilibrium
-bring about the most evolutionary change

Natural Selection

-differential success in reproductive results in certain alleles being passed to the next generation in greater proportions

Genetic Drift

-random change in allele frequencies that occurs in small populations
-some alleles get passed on disproportionately due to chance
-most significant in small populations
-tends to reduce genetic variation through losses of alleles
-can cause harmful alleles to become fixed

Gene Flow

-individuals entering and leaving the population
(immigration and emigration)
-the movement of alleles among populations
(pollen carries between populations)
-can increase or decrease the fitness of a population depending on which genes are involved
-important agent in evolutionary change in modern human populations

Founder Effect

-few individuals become isolated from a larger population.
-if the population remains small it may be further affected by genetic drift

Bottleneck Effect

-drastic reduction in population sized due to a sudden environmental change
-resulting gene pool may no longer be reflective of the original gene pool
-if the population remains small it may be further affected by genetic drift

Adaptive Evolution

-increase in frequency of beneficial alleles and decrease in deleterious alleles due to selection

3 modes of natural selection

1. Directional
2. Disruptive
3. Stabilizing

Directional Selection

-favors individuals at one end of the phenotypic range

Disruptive Selection

-favors individuals at both extremes of the phenotypic range

Stabilizing Selection

-favors intermediate variants and acts against extreme phenotypes

Sexual Selection

-natural selection for mating success
-correlated with better overall genotype
-can result in sexual dimorphism

Sexual Dimorphism

-differences in physical characteristics between males and females of the same species.

Why can't natural selection fashion perfect organisms?

-selection can act only on existing variation
-evolution is limited by historical constraints
-adaptions are often compromises
-environmental change

Speciation

-the process by which one species splits into two or more species
-forms a conceptual bridge between microevolution and macroevolution

Microevolution

-changes in allele frequency in a population over time

Macroevolution

-broad patterns of evolutionary change above the species level

Biological Species Concept

-a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
-don't breed successfully with other populations

Reproductive Isolation

-existence of biological barriers that impede two species from producing viable, fertile offsprings
-species' boundaries
-can be classified by whether barriers act before or after fertilization

Prezygotic Barriers

block fertilization from occurring by:
1. impeding different species from attempting to mate
2. preventing successful completion of mating
3. hindering fertilization if mating is successful

Habitat Isolation

-two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers
- ex. aquatic and terrestrial garter snakes

Temporal Isolation

-species that breed at different times of the day, different seasons, or different years cannot mix their gametes
-ex. mating season of skunk species

Behavioral Isolation

-courtship rituals and other unique behaviors unique to a species are effective barriers
-blue-footed boobies display

Mechanical Isolation

-morphological differences prevent successful mating
-ex. snail species' reproductive anatomy

Gametic Isolation

-sperm of one species may not be able to fertilize eggs or another species
-ex. sea urchin gametes

Postzygotic Barriers

-prevent the hybrid zygote from developing into a viable, fertile adult by:
1. reduced hybrid viability
2. reduced hybrid fertility
3. hybrid breakdown

Reduced Hybrid Viability

-genes of the different parent species may interact and impair the hybrid's development or survival

Reduced Hybrid Fertility

-even if hybrids are vigorous, they may be sterile
-ex. donkey x horse = mule (mules are sterile)

Hybrids

-offsprings of crosses between different species

Hybrid Breakdown

-some first-generation hybrids are fertile, but when they mate with another species or with either parent species, the offspring of the next generation are feeble or sterile.
-strains of cultivated rice accumulating bad alleles

Limitations of the Biological Species Concept

-cannot be applied to fossils or asexual organisms (all prokaryotes)
-emphasizes the absence of gene flow (gene flow can sometimes occur between distinct species)
-ex. grizzly bears and polar bears can rarely mate to produce "grolar bears"

Morphological Species Concept

-defines species by structural features
-applies to sexual and asexual species but relies on subjective criteria

Ecological Species Concept

-views species in terms of their ecological niche
-applies to sexual and asexual species and emphasizes the role of disruptive selection

Phylogenetic Species Concept

-defines a species as the smallest group of individuals on a phylogenetic tree (smallest branch)
-applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species

Speciation can occur in two ways:

1. allopatric speciation
2. sympatric speciation