Biology Notes. Chapter 13 and Chapter 16

Ch. 13 Evolution: change in genetic composition of populations over time; Darwin is credited with coming up with the mechanism for evolution Evolutionary theory: is the understanding and application of the processes of evolutionary change to biological problems Darwin Observations: Observed that offspring aren’t identical to one another or their parents. Also observed that most species are born to survive to reproduce. Darwins’s theory for evolutionary change: 1. Species change over time 2. Divergent species share a common ancestor 3. Mechanism that produces change is natural selection. Natural Selection: nature chooses the traits that provide the best chances of survival. Artificial Selection: humans choose, ex: Researcher breed yeast to withstand high concentrations of ethanol Evolution: refers specifically to changes in the genetic makeup of populations over time Population: a group of individuals of a single species that live and interbreed in a particular geographic area at the same time. Individuals do not evolve; populations do. Mutation: any change in nucleotide sequences. Can be beneficial, have no effect, or be deleterious (causing harm or damage). Mutations can lead to a lot of genetic diversity in a population. Gene pool: sum of all copies of all allele at all loci in a population Allele frequency—proportion of each allele in the gene pool Genotype frequency—proportion of each genotype among individuals in the population Adaptation- Moths with wing tails produced a certain flutter that could help avoid bats Gene Flow- new genes or different genes are flowing from one place to another throughout populations. Arrival of new individuals or new gametes into a population. Ex: flock of birds Genetic Drift- random changes in allele frequencies from one generation to another. Change in Aa, and increase in aa, AA/Ex: Population Bottleneck; when a flood wipes up a lot of animals in an environment. Population can lose a lot of genetic variation. Founder Effect- a small population is transported to a new environment. There is only a small portion of alleles that was in the original population. Decreased variation in the allele. Ex: flock of birds Nonrandom mating - individuals prefer to mate with individuals of the same genotype. Sexual Selection- individuals of one sex mate prefer to mate with particular individuals of the opposite sex rather than at random/ more likely to reproduce, but less likely to survive Hardy-Weinburg equilibrium- there has to be five conditions; random mating, no mutation, no gene flow, and no selection of genotypes. 5 Processes of Evolution 1. 2. 3. 4. 5. Mutation Selection Gene flow Genetic Drift Non random mating Hardy-Weinburg Equilibrium 1. 2. 3. 4. 5. No mutation No selection No gene flow Infinite population size Random mating Processes of Evolution and Hardy Weinberg Equilibrium are the opposite of each other Fitness- reproductive contribution of a phenotype to subsequent generations relative to the contributions of other phenotypes Qualitative- black vs. white; discrete physical characteristics Quantitative- body size of individuals; measurable in numbers Types of Selections Stabilizing-favors average individuals Directional (Positive)- favors individuals that vary in one direction from the mean Disruptive- favors both; can result in increased variation and bimodal distribution of traits; going away from the mean or average. Frequency-dependent selection- maintains genetic variation. Ex: left mouth and right mouth fish are both favored. The host fish can be attacked from either side. Heterozygote Advantage- in changing conditions, heterozygous individuals are likely to outperform homozygotes. Different alleles of a gene may be advantageous under different environmental conditions 1. Over time, there will be disruptive selection where the individuals that vary in one direction from the mean are favored. As the population grows on the land, there will be competition for food. Some sparrows will stabilize in eating the small seeded tree and a large seeded bush. Ch. 16 Species- groups of organisms that share a suite of genetic and morphological attributes. Are reproductively isolated from other such groups. Speciation- divergence of biological lineages and emergence of reproductive isolation between lineages Linnaeus- described species based on their appearance; the morphological species concept Limitations: members of the same species do not always look alike. Cryptic Species- classify as the same species, but there not. two or more species that are morphologically indistinguishable but do not interbreed. Second species concept- Biological species concept- species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups. Reproductive Isolation- two groups of organisms can no longer exchange genes Lineage species concept- species as branches on the tree of life Lineage- an ancestor- descendant series of populations followed over time Linnaeus morphological- The frogs both have different appearances. One is lighter than the other. They can be descendants or ancestors of one another. Are they breeding together. Are their offspring similar to each other? How do we see the formation of a new species? Allopatric speciation- when populations are separated by a physical or geographic barrier between two populations. Over time, they separate into two different species This can happen when continents drift or glaciers advance and retreat. Sister Species- may exist on opposite sides of a geographic barrier. May look similar because they share a common ancestor, but they are going to have different gene expressions. Ex: One species may have more body tissue to help it conserve energy. Niche- a certain part of the environment that the species can thrive in; functional role that that an organism plays within an environment Sympatric speciation- speciation without physical isolation. Ex: in apple maggot flies, one group prefers to lay eggs on apples. They are partially reproductively isolated. Originally were the same species, but then branched off into two based on their preferences. They no longer share their genes with each other. If reproductive isolation is incomplete, hybridization can occur. Hybrids can have less chances of survival and lower chances of reproducing. This can result in reinforcement of isolating mechanisms. Two Isolating Mechanisms- prevents hybrids from being produced Prezygotic Isolating Mechanisms- prevents hybridization from occurring ● ● ● Mechanical- differences in sizes and shapes of reproductive organs. In plants, it may involve pollinators Temporal isolation- species may breed at different times of year or day. Behavioral- individuals reject or fail to recognize mating behaviors of other species Postzygotic- reduces fitness of hybrid offspring Habitat Isolation- two closely related species evolve preferences for living or mating in different habitats Ex: apple maggot flies and Lake Malawi cichlids Gametic Isolation- sperm and eggs of different species will not fuse; important for aquatic animals that release gametes into the water If reproductive isolation is incomplete, hybrid zones may form where population ranges overlap. Rates of speciation vary greatly. Many factors influence the likelihood that a lineage will split. 1. Diet specialization-populations with specialized diets are more likely to diverge. More likely to branch off and form their own species. 2. Pollination- speciation rates are higher in animal pollinated than wind pollinated plants; are correlated with pollinator specialization. 3. Sexual Selection- results in high rates of speciation-especially in birds with polygynous mating systems and high degrees of sexual dimorphism. Dispersal ability- snails are slow moving, and they form a new species based on where a mountain is; which mountain helps them travel farther or better? Speciation rates can be faster in species with poor dispersal abilities because they can be separated by narrow barriers. Prezygotic Isolating Mechanisms Mechanical- differences in sizes and shapes of reproductive organs. In plants it may involve pollinators. Temporal- species may breed at different times of year or different times of day BehavioralHabitat- two closely related species evolve preferences for living or mating different habitats Gametic Postreduced zygote ability Hybrid infertility offspring of two related species are incapable of reproducing Evolutionary radiation- rapid speciation can lead to this. Proliferation of many species from a single ancestor Adaptive radiation-if the resulting species live in a wide array of environments; land snails in Hawaii