Bio Ii

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Speciation

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the process by which one species splits into two or more species.

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Biological species concept

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defines a species as a group of populations whose members have the potential to interbreed in nature and produces viable, fertile offspring, but do not produce viable, fertile offspring with member of other such groups.

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Prezygotic barriers

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blocks fertilization from occuring

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Postzygotic barriers

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reproductive isolation occurs after the hybrid zygote is formed.

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Habitat isolation

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species occupy different habitats with in the same area and therefore rarely encounter each other.

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Temporal Isolation

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species that breed during different times of the day, season, or years.

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Behavioral isolation

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courtship rituals that attract mates and enable mate recognition.

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Mechanical isolation

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mating is attempted, but morphological differences prevent a successful completion.

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Gametic Isolation

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mating is attempted, but the sperm of one species is unable to fertilize the egg of another species.

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Reduced hybrid viability

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zygote forms but either the embryo does not develop or the offspring doesn't survive in its environment.

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Reduced hybrid fertility

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the hybrid is healthy, but is infertile and cannot produce offspring.

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Hybrid breakdown

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when a viable, fertile hybrid reproduces, but their offspring are feeble or sterile.

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Morphological species concept

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characterizes species by body shape and structure features.

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Ecological species concept

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defines species based on ecological nice.

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Philogenetic species concept

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defines species as the smallest group of individuals that share a common ancestor.

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Allopatric speciation

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speciation occurs because gene flow is interrupted when a population beomes geographically isolated.

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Sympatric Speciation

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Speciation occurs without geographic seperation

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Polyploidy

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an accident in cell division that results in extra set of chromosomes.

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Habitat differentiation

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genetic factors enable a supopulation to exploit a habitat or resource not used by the parent population.

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Sexual Selection

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a subset of the population starts choosing the opposite sex based on specific characteristics.

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Hybrid zones

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a region in which members of different species meet and mate, producing some offspring of mixed ancestry

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Hybrid zone outcome: Reinforcement

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process of natural selection strengthening the prezygotic barriers reducing the chances of hybrid formation.

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Hybrid zone outcome: Fusion

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weak reproductive barriers increase gene flow between the two species causing the two hybrid species to fuse into single species.

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Hybrid zone outcome: Stability

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hybrids continue to be produced because the hybrids survive and/or reproduce better than the parent species.

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Punctuated equilibrium

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periods of stasis followed by sudden change.

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Gradualism

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change occurs gradually over long periods of time.

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Macroevolution

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broad pattern of evolution above the species level.

is often revealed through the fossil record.

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Radiometric dating

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a technique of dating rocks and fossils based on the fixed rate of radioactive isotope decay.

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Half-life

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the amount of time required for 50% of the parent isotope to decay.

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Prokaryotes

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The first-single celled organisms were _____, organisms without membrane-bound organelles.

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Eukaryotes

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organisms with membrane-bound organelles, evolved through:

Infolding of plasma membrane

Endosymbiotic theory – cell engulfing a prokaryote

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Why is multicellularity important?

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Multicellularity led to the great innovation of specialization.

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What lead to multicellular organisms?

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Colonial unicellular organisms

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Cambrian explosion

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a burst of evolutionary change that occurred in a short geological period, which includes the appearance of many present-day animal phyla.

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colonized land about 420 million years ago

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Plants, fungi, and arthropods

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colonized land about 365 million years ago

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vertebrates, specifically tetrapods

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Continental drift

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the process in which the earth’s mantle causes the continental plates to move.

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Adaptive radiation

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periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles (niches) in their communities.

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Archaeopteryx

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the transitional species between dinosaurs and birds

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Pakicetus, Ambulocetus, & Rodhocetus

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fill the gaps between whales and their hoofed mammal ancestors

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Tinkerer Vs. Engineer theory

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suggests that natural selection is like a tinkerer working with whatever material is available, rather than an engineer who can design and build the best possible structure.

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Taxonomy

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discipline in which organisms are named and classified

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Taxa (pl. taxon)

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taxonomic unit at any level.

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Binomial nomenclature

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the scientific name of an organism that consists of a genus and species.

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Systematics

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a disciline focused on classifying organisms and determining their evolutionary relationships.

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Phylogeny

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the evolutionary history of a species or group of species.

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Phylogenetic tree

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branching diagram that represents the evolutionary history of a group of organisms.

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Phylogenetic tree Nodes

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represent common ancestors.

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Phylogenetic tree Branch point

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where lineages diverge

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Phylogenetic tree Polytomy

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a branch point where more than two taxa emerge.

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Phylogenetic tree Sister taxa

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groups that share an immediate common ancestor

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Phylogenetic tree Basal Taxon

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lineage that diverges early in the history of the group.

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Homology

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genotypic and phenotypic similarities due to sharing ancestry.

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Analogy (homoplasies)

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phenotypic similarities, but no shared ancestry.

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Convergent evolution

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the process of similar adaptations evolving in organisms from different evolutionary lineages due to similar environmental pressures.

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Synapomorphies

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shared derived characteristics that represent departure from the ancestor.

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Symplesiomorphies

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shared ancestral characteristics that evolved prior to the most recent common ancestor.

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Principle of Maximum Parsimony

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should support the hypothesis with the fewest evolutionary assumptions.

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Principle of Maximum likelihood

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given certain probability rules about how DNA sequences change over time, the hypothesis that reflects the most likely sequence of evolutionary events should be supported.

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Monophyletic

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a group that consists of the ancestral species and all of its descendants

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Paraphyletic

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a group that consists of the ancestral species and some, but not all, of its descendants.

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Polyphyletic

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a group that doesn't include the closest common ancestor.

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Evolution according to Darwin

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Descent with modification

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Darwin Adaptation

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inherited characteristics of organisms that enhance their fitness in specific environments

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Darwin Fitness

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quantifiable measure of survival and reproductive success

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Darwin natural selection

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the process in which individuals that have certain inherited traits tend to have higher fitness because of these adaptations

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For natural selection to work, three aspects of variation must occur:

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1. Must be present in population

2. Must affect fitness

3. Must be inherited

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Artificial selection

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the process in which humans modify organism by selecting & breeding organisms with certain traits.

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Homologous Structures

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structures in different species that have a general theme because of common ancestry, but the structures may vary in form and function

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Vestigial structures

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remnants of structures that served an important function in the ancestor but not in the current organism

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Evidence for Evolution

DNA and ATP

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all organisms contain genetic information in the form of DNA. All organisms use ATP for energy use

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Biogeography

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the geographic distribution of species

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Convergent evolution

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the independant evolution of similar features in different lineages due to similar environmental pressures.

Homoplasy - similar characteristics but do not share a common ancestor

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Microevolution

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The change in allele frequencies in a population over time

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Populations

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All the individuals of one species in a particular area

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Genes

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A discrete unit of hereditary information consisting of a specific nucleotide sequence in dna

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Genotype

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Genetic makeup, or set of alleles, of an organism

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Allele

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any alternative versions of a gene that may produce distinguishable phenotypic effects

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Phenotype

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observable traits of an organism that are determined by a genotype

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Genetic variation

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differences among individuals in the composition of their genes or other DNA segments

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Phenotypic plasticity

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variations in appearance due to environmental influences

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Gene Variation - Nucleotide variability

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at molecular level of dna

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Gene Variation - Gene variability

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at the whole gene level, which is quantified by average heterozygosity

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Geographic v ariation

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differences in the genetic composition of seperate populations

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Cline

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a graded change in character along a geographic axis

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Hardy-Weinberg Principle

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suggests that the original proportions of genotypes within a population should remain constant, if 5 assumptions are met

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Hardy-Weinberg assumptions

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1) no mutations

2) no gene flow

3) random mating must occur

4) population size is large

5) no selection occurs

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Hardy Weinberg Equilibrium

Allele Frequencies equation

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p + q = 1

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Hardy Weinberg Equilibrium

Genotype Frequencies equation

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

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What can alter allele frequencies?

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1) Genetic Drift

2) Gene flow

3) Natural selection

4) Sexual selection

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Genetic drift "Founder effect"

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Few individuals become isolated from a larger population

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Genetic drift "Bottleneck effect"

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Reduction of population size due to a sudden change in environment

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Gene flow

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Movement of alleles into or out of a population

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Emigration

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movement of individuals out of a population

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Natural Selection

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the process in which individuals that have certain inherited traits tend to have higher fitness because of those adaptations

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Relative fitness

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contribution that an individual makes to the gene pool of the next generation relative to the contributions of other individuals

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Three ways natural selection can alter frequency distribution

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1) Directional

2) Disruptive

3) Stabilizing

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Directional frequency distribution

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One end of distribution is favored

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Disruptive frequency distribution

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both ends of the distribution are favored

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Stabilizing frequency distribution

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intermediates of the distribution are favored

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Sexual selection

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a form of selection in which individuals with certain phenotypes are more likely than others to obtain mates

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Intrasexual selection

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individuals of the same sex compete for access to mates

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Intersexual selection

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individuals of one sex choose their mates of the opposite sex

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Balancing selection

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occurs when natural selection maintains variation in the population

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Two ways balancing selection can occur

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1) heterozygote advantage

2) frequency dependant selection

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Heterozygote advantage

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heterozygotes have greater fitness than both homozygotes

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Frequency-dependant selection

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fitness of phenotype depends on how common it is in the population

ex: left and right mouthed suckers

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Why Natural Selecton Cannot Fashion Perfect Organisms?

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1) Selection can at only on existing variation

2) Evolution is limited by historical restraints

3) Adaptations are often compromises

4) Chance, natural selection, & the environment interact