Natural Selection

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

For natural selection to work: (3 aspects must occur)

Variation: 1. must be present in the population
2. must affect fitness
3. must be inherited

Artificial selection

the process in which humans modify organisms by selecting and breeding organisms with certain traits

Homologous structures

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

Vestigial structures

remnants of structures that serve an important function in the ancestor, but not in the present organism

Biogeography

the geographic distribution of species

Convergent evolution

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

microevolution

The change in allele frequencies in a population over time

populations

all the individuals of one species in a particular area

Genes

a discrete unit of hereditary info. consisting of a specific nucleotide sequence in DNA

Genotype

the genetic makeup, or set of alleles, of an organism

Allele

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

Phenotype

observable traits of an organism that are determined by genotype

Dominant phenotype

homozygous dominant or heterozygous genotype

Recessive phenotype

homozygous recessive genotype

genetic variation

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

Phenotypic plasticity

variations in appearance due to environmental influences

2 ways to measure genetic variation:

1. nucleotide variability- at the molecular level of DNA
2. gene variability- at the whole gene level, which is quantified by average heterozygosity

Geographic variation

differences in the genetic composition of separate populations

cline

a graded change in character along a geographic axis

Sources of genetic variation

1. Formation of new alleles through mutation
2. Altering gene number or position through chromosomal changes that delete, disrupt, or rearrange loci
3. Rapid reproduction can increase mutation rates
4. Sexual reproduction due to: crossing over, independent assortment of alleles, fertilization

Hardy-Weinberg principle: original proportions of genotypes within a population will remain the same if:

1. no mutations
2. no gene flow
3. random mating occurs
4. population size is large
5. no selection occurs

Hardy Weinberg allele frequency equation

p+q=1

Hardy Weinberg genotype frequency equation

p(squared)+ 2pq + q(squared)=1

Genetic drift

chance events that can cause unpredictable fluctuations in allele frequencies from one generation to the next

Genetic drift example: Founder effect

When a few individuals become isolated from a larger population

Genetic drift example: Bottleneck effect

a reduction of population size due to a sudden change in environment

Gene flow

movement of alleles into or out of a population

immigration- move into
emigration- move out of

Natural Selection

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

Relative fitness

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

Directional-

natural selecting can alter frequency distribution

one end of distribution is favored

Disruptive-

natural selecting can alter frequency distribution

both ends of the distribution are favored

Stabilizing-

natural selecting can alter frequency distribution

intermediates of the distribution are favored

Sexual selection

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

Intra-sexual selection

individuals of the same sex compete for access to mates

Inter-sexual selection

individuals of one sex choose their mates of the opposite sex

Balancing selection

occurs when natural selection maintains variation in the population
2 ways: Heterozygote advantage
Frequency dependent selection

Heterozygotes advantage

heterozygotes have a greater fitness than both homozygotes

Frequency-dependent selection

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

Why natural selection cannot fashion perfect organisms????

1. selection can act only on existing variations
2. evolution is limited by historical constraints
3. adaptations are often compromises
4. chance, natural selection, and the environment interact

Speciation

the process by which one species splits into 2 or more species

Biological species concept

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

Reproductive isolation

the existence of biological factors(barriers) that impede members of 2 species from interbreeding and producing viable, fertile offspring

pre-zygotic barrier

block fertilization from occuring

Post-zygotic barriers

reproductive isolation occurs after the hybrid zygote is formed

Habitat isolation

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

Temporal isolation

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

Behavioral isolation

courtship rituals that attracts mates and enables mate recognition

Mechanical isolation

Mating is attempted, but morphological differences prevent a successful completion

Gametic isolation

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

Reduced hybrid viability

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

Reduced hybrid fertility

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

Hybrid breakdown

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

Morphological species concept-

characterizes species by body shape and structure features

Ecological Species concept

defines species based on ecological niche

Phylogenetic species concept

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

Allopatric speciation

occurs because gene flow is interrupted when a population becomes geographically isolated

Sympatric speciation

speciation occurs without geographic separation

Polyploidy

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

Habitat differentiation

genetic factors enable a subpopulation to exploit a habitat or resource not used by the present population

Sexual selection

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

Hybrid zones

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

Reinforcement

process of natural selection strengthening the pre-zygotic barriers reducing the chances of hybrid formation

Fusion

weak reproductive barriers increase gene flow between the 2 species causing the 2 hybrid species to fuse into single species

Stability

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

Punctuated equilibrium

periods of stasis followed by sudden change

Gradualism

change occurs gradually over long periods of time

Macroevolution

broad pattern of evolution above the species level
-revealed through fossil record

4 main stages the could have produced the first sell:

1. the abiotic synthesis of small organic molecules, such as AA and nitrogenous bases
2. the joining of these small molecules into macromolecules
3. the packaging of these molecules into protocell droplets with membranes that maintained internal chemistry different from the surroundings
4. The origin of the self-replicating molecules that eventually made inheritance possible

Radiometric dating

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

Half life

Amount of time required for 50% of the parent isotope to decay

Eukaryotes, organisms with membrane-bound organelles, evolved through:

-infolding of plasma membrane--created ER, nuclear membrane
-endosymbiotic theory-cell engulfing a prokaryote---created mitochondria, chloroplasts, plastids

Why is Multicellularity important?
hypothesis?

Led to the great innovation of specialization
- Colonial unicellular organisms let to multicellular organisms

cambrian explosion

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

Continental drift

process in which the earth's mantle causes the continental plates to move
-promotes allopatric speciation on a grand scale

Adaptive radiation

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

Horse fossils show 3 trends:

1. larger size
2.more complex molar teeth
3. fewer toes

Permian period

most extensive loss. 96% of plants and animal species perished

Cretaceous period

most famous and well studies. Caused by meteorite causing mass forest fire and smoke blocked sun, dinosaurs died off while placental mammals flourished

Taxonomy

disciplin in which organisms are named and classified

Taxa

taxonomic unit at any level

Binomial nomenclature

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

Systematics

a discipline focused on classifying organisms and determining their evolutionary relationships

Phylogeny

the evolutionary history of a species or group of species

phylogenetic tree

branching diagram that represent the evolutionary history of a group of organisms

nodes

represent common ancestor

branch point

where lineages diverge

polytomy

a branch point where more than 2 taxa emerge

sister taxa

groups that share an immediate common ancestor

Basal taxon

lineage that diverges early in the history of the group

Homology

genotypic and phenotypic similarities due to sharing ancestry

Analogy

Phenotypic similarities, but no shared ancestry

Convergent evolution

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

Outgroup

a taxa that is closely related to the group of organisms that you are studying, but are not part of your study group

synaphories

shared derived characters that represent departure from the ancestor

Sympleslomorphies

shared ancestral characters that evolved prior to the most recent common ancestor

Monophyletic

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

Paraphyletic

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

Polyphyletic

a group that doesn't include the closest common ancestor

3 domains?

Archaea
Bacteria
Eukarya

kingdoms of Eukarya:

Plantae
Fungi
Animalia
Protista