Chapter 17 & 18 Work

Derek Lee

Ap Biology

Period 4

Chapters 17 & 18 Work

II.

1.      Prophase I, Allele Frequency- Allele frequencies are those relative abundance of alleles of a give gene among all individuals of a population that can start from a theoretical reference point, genetic equilibrium, when a population is not evolving with respect to that locus. However, this genetic equilibrium and thus allele frequency can be thrown off by natural selection, genetic drift, natural selection, or the wild card of mutations; some of which arise during prophase I of meiosis due to crossing over during prophase I, independent assortment, etc.

2.      Natural Selection, analogous structures- Analogous structures are those with dissimilar body parts that have become similar in structure, function, or both in lineages that are not closely related but were subjected to similar pressures. Regardless, such creatures evolved over time via mutations that occur in populations in response to the environment, in this case environmental pressures. These evolutions may result from natural selection and the passing of favorable traits based on environmental pressures.

3.      Bottleneck and Gene pool- Bottleneck is a drastic reduction in population size brought about by severe pressure. A gene pool is the pool of genetic resources for a population. If large numbers of a population are wiped out, this decreases the gene pool and thus genetic variation.

4.      Balance polymorphism and search image-Balanced selection occurs when two or more alleles of a gene are being maintained at relatively high frequencies in the population, their persistence is balanced polymorphism. Such is seen with certain genetic disorders such as sickle-cell anemia. Search images may how this distribution of disease over its density with i.e. a country.

III.

1.      - Observation: Natural populations have an inherent reproductive capacity to increase in size over time.

-Observation: No population can indefinitely grow in size, because its individuals will run out of resources-food, space, etc.

-Inference: Individuals will end of competing for dwindling resources.

-Observation: Individuals share a pool of heritable information about traits, encoded in genes.

-Observation: Variations in traits start with alleles, slightly different molecular forms of genes that arise through mutations

-Inferences: Forms of traits are more suited for the individual to survive. These alleles for adaptive forms become more frequent and lead to increased fitness- an increase in adaptation to the environment as measured by the genetic contribution to future generations.

-Conclusions: Natural selection is the outcome of differences in reproduction among individuals of a population that vary in shared traits.

2. –Origin of Earth’s crust, first atmosphere, first seas. Chemical, molecular evolution leads to origin of life from proto-cells to anaerobic prokaryotic cells

- Origin of photosynthetic prokaryotic cells.

-Oxygen accumulates in atmosphere. Origin of aerobic metabolism. Origin of eukaryotic cells. Divergences of lead to eukaryotic cells, then protists, fungi, plants, and animals.

-Major crustal movements. Ice ages. Mass extinction of many marine species. Vast swamps form. Origin of vascular plants. Adaptive radiation of fishes continues. Origin of amphibians.

-Recurring ice ages. On land, adaptive radiations of insects, amphibians. Spore-bearing plants dominate; cone-bearing gymnosperms present. Origin of reptiles.

-Adaptive radiations of marine invertebrates, fishes, dinosaurs, Gymnosperms dominate land plants. Origin of mammals.

-Early Cretaceous Mesozoic and Cenozoic tertiary – Major crustal movements, collisions, mountain building, Tropics, subtropics extended pole ward. When climate cools, dry woodlands, grasslands emerge. Adaptive radiations of flowering plants, insects and mammals, and origin of angiosperms.

3. Evolution does not happen on the individual level, but happens in populations over time. Evolution is drive by the environment, which favor certain traits. Thus variation is absolutely necessary for evolution to take place. The environment doesn’t create the adaptations, it simply favors some and not others. Variations are differences in traits, which are determined by genes. More specifically, the “variations” we are speaking of are variations in the frequency of alleles in a population. An individual may not just evolve: i.e. grow longer arms merely out of necessity but rather through populations whose environment favors their traits/adaptations which help them survive and is thus passed on from generation to generation (speciation).

4. Gene mutations- changes in the sequence of DNA bases within a gene. Frame shift and point/substitution mutations.

Crossing over at meiosis I (puts novel combinations of alleles in chromosomes)- producing genetic variation some of which may produce a mutation proving beneficial leading to genetic variation.

-Independent assortment at meiosis I (puts mixes of maternal and paternal chromosomes in gametes) Chromosomes are inherited independently of one another.

-Fertilization (combines alleles from two parents)- for sexually reproducing species, the population of individuals that are interbreeding, reproductively isolated from other species producing fertile offspring. Have traits which show qualitative and quantitative differences for a specified trait.

-Change in chromosome number or structure (loss, duplication, or repositioning of genes)- thought often leads to severe mental or physical impairments results from mutation.

5. p2 (AA) + 2pq (Aa) + q2 (aa) = 1.0

P and q are the frequencies of alleles A and q. It defines the frequency of a dominant and a recessive allele for a gene that controls a particular trait in a population. The frequencies of A and a must add up to 1.0.