BIOLOGY EXAM 4

Evolution

a heritable change in a population of organisms over generations

Species & who proposed the idea

Species is a group of related organisms that interbreed and produce fertile offspring. John Ray

factors that led Darwin & Wallace to the theory of evolution. “Great Fossils Verify Traits”

Geographic distribution of species, Fossil record, Variation in traits within populations, The influence of malthus idea on population growth & resource limitation

Natural selection

organisms with traits that help them survive in their environment are more likely to re produce and pass on those traits.

Different types of evidence for evolutionary change. “Silly Scientists Believe Cool Fossils Help”

Studies of natural selection, Selective breeding, Biogeography, Convergent traits, Fossil record, Homologies

Studies of natural selection

traits that help survival get passed down in real environments

Selective breeding

Humans pick traits in domesticated animals or plants.

Biogeography

Where species live and how they’re spaced out.

Convergent Traits

Different species evolve similar traits because they live in similar environments

Fossil record

Fossils show gradual changes over long periods of time

Homologies

similar traits because of a common ancestor (body, development, DNA)

Different types of Homologies.

“All Dogs Move”

Anatomical, Developmental, Molecular

Anatomical Homologies

Similar body structures from a common ancestor. (human arm, bat wing, whale fin bones)

Developmental Homologies

Similar embryonic stages (embryos of fish, birds, and humans look alike early on)

Molecular Homologies

Similar DNA, proteins, and genes (like humans and chimpanzees)

Define a gene pool

A gene pool is the complete set of all alleles for every gene present in a population

Allele Frequency

proportion of a specific allele in the gene pool compared to the total numbers of alleles for that gene. (small: A or a)

Genotype frequency

the proportion of individuals in a population with a specific genotype (group: AA or Aa)

Conditions that must be met for a population to be in Hardy-Weinberg equilibrium. M.R.N.G

No new mutations, Random mating, No natural selection, large population size, No gene flow

Factors that cause micro evolution to occur. “My Giant Giraffe Never Naps”

Mutation, Genetic drift, Gene flow, Non random mating, Natural selection

How can natural selection result in a population that is better adapted to its environment and more successful at reproduction

traits help survival→ more reproduction→ traits spread.

over time; the population adapts to its surroundings

4 patterns of Natural selection.

“D. S. D. B

Directional selection, Stabilizing selection, Disruptive selection, Balancing selection

Directional selection

shifts the population toward one extreme

Stabilizing selection

keeps the population centered around an average trait

Disruptive selection

creates two extremes

Balancing selection

maintains genetic diversity through various mechanisms

Define sexual selection

a type of natural selection where certain traits increase an individual’s chances of obtaining mates and reproducing. does not have to have survival traits. (peacock feathers: males with larger more colorful feathers attract more females)

INTRAsexual

competition between individuals of the same sex for access to mates. (male lions fighting with each-other for dominance)

INTERsexual

members of one sex (typically females) choose their mates based on certain traits or behaviors. (female peacocks choose males with the most colorful tail feathers)

define genetic drift

random changes in allele frequencies due to chance (like flipping a coin)

how does genetic drift effect allele frequencies

over time, some alleles will be randomly lost from the population due to chance. random change may lead to one allele becoming the only one present in the population.

Bottleneck effect

a disaster wipes out a large portion of a population. (bit reduction of the population size)

Founder effect

a small group of individuals leaves the larger population and forms a new population. (new beginnings)

how does gene flow affect genetic variation in neighboring populations

gene flow is the movement of alleles between populations dude to migration or reproduction.

affects: increased genetic diversity, reduced genetic differences, and can prevent speciation

Define inbreeding and explain how it may have detrimental consequences

the mating between genetically related individuals. this can increase the chance that harmful recessive alleles will be expressed, which normally is hidden in heterozygotes. Homozygosity is raised and heterozygotes is lowered

The characteristics that biologists use to distinguish different species.

“Many Rabbits Make Excellent Eggs”

Morphological traits (physical features), Reproductive Isolation (whether two groups can successfully interbreed), Molecular features (difference in DNA, gene order, or chromosome structure), Ecological factors (species are identified by the habitat), Evolutionary relationships (species are identified based on shared ancestors)

define subspecies

same species, but separated by space (began tiger, Siberian tigers are all tigers, but adapted to different regions)

define horizontal gene transfer

genes are passed between organisms in a non-reproductive way

different species concepts

“Big Elephants Eat Grapes

Biological, Evolutionary lineage, Ecological, Genera lineage.

Biological species concept

two populations that do not interbreed or produce infertile offspring. members are reproductively isolated from other species.

Evolutionary lineage concept

a line of decent that evolves separately from others.

Ecological species concept

defined by its unique role or habitat

General lineage concept

a population of organisms evolving independently

Prezygotic isolation

prevents mating or fertilization from happening. (prevents zygote)

postzygotic isolation

fertilization happens but the offspring dies early, has low fitness or developmental problems. (problems after zygote)

how an adaptation to feeding may have promoted reproductive isolation in finches

finches with different beak sizes (large beaks for harder seeds). Over time, finches with similar beak sizes may mate more because they share the same feeding habits, leading to assortative mating.

Beak size= feeding habits= mating habits= isolation

how does allopatric speciation happen

allopatric speciation happens when a population is geographically isolated (island). over time they evolve independently due to different environmental pressures, genetic drift, and mutations.

how does allopatric speciation leads to adaptive radiation

a single ancestral species rapidly diversifies into many new species, each adapted to a different ecological niche (species with different feeding habits or sizes)

define hybrid zone. possible consequences of interbreeding within a hybrid zone

an area where two closely related species or populations come into contact and are able to interbreed, producing hybrid offspring. Consequences: reproductive barriers are strengthened, reproductive barriers weaken and the two merge back into one species, hybrid offspring continues to be produced but no further change occurs.

four different mechanisms of sympatric speciation

P-H-S-N

Polyploidy, Habitat differentiation, Sexual selection, Natural selection

Polyploidy

organism ends up with more than two sets of chromosomes

Habitat differentiation

different parts of the habitat become occupied by different groups within the same population, leading to reproductive isolation

Sexual selection

different mate preferences within the same population can lead to reproductive isolation

Natural selection

different predators or resources may cause populations to adapt in different ways

Macroevolution

large scale evolution that occurs over long periods of time. major changes like formation of new species, leads to development of new lineages.

Microevolution

small scale evolution that happens with a single population. involves changes in allele frequencies in a populations gene pool from one gen to the next. (genetic drift)

How fossils are formed

Four S’s

Sand, Shell, Sediment, Stone

organisms are buried in sand and shells, layers of sediment build up, and over time turns into stone (fossils)

Factors that affect fossil completeness

“OATS”

Organism type (hard parts like bones), Anatomy/Size (larger organisms), Time (fossils require years to form), Specific environments (dry or polar environments preserve animals)