chapter 22,23,24 Flashcards
Evolution
change in gentic compostion of a population over generations
Adaptation
traits that enchance survival and reproduction in given environment.
Natural selection
where indivuals with favorable traits survive and reproduce more successfully
- Describe how the following people influenced Darwin: Linneus Lyell Hutton Cuvier Lamarck Malthus
- Linnaeus- helped with systematic framework for organizing species. This helped Darwin understand the relationships between diff organisms and laid the groundwork for his ideas on common descent.
- Lyell- proposed earths geological features were slow not sudden. Sm changes could lead to significant things overtime.
- Hutton- deep time and gradual process. Helped him realized the timescales for evolutionary change.
- Cuvier- work on fossil records and extinction. Helped Darwin with natural selection.
- Malthus- population growth and struggle for existence. Helped him understand competition and survival and develop natural selection
- Explain how the principle of gradualism and Charles Lyell’s theory of uniformitarianism influenced Darwin’s ideas about evolution
- The principle of gradualism suggests that changes occur slowly and incrementally over long periods, was central to Darwin’s theory. This idea was supported by lyells theory of uniformitarism which proposed geological changes. Darwin applied these concepts to make his own biological theory
Lamarcks model
it proposed that inhetiance of acquired charcteristics meaning traits devolped during an organism’s life time could be passed on. It was rejected.
Principle of common descent
all species share a common ancestor and have diverged over time through gradual changes.
Key concepts of evolutionary theory
indivual fitness ability to surrive and reproduce. Variation- differences in traits amoung indivuals. Heritability- traits must be passed to offspring. Natural selection- some traits increase survival and reproduction. No goal oriented- evolution is not working towards a specific outcome.
Evidence for evolution
biogeography- species distribution shows common ancestry. Fossil record- shows gradual change over time. Comparative anatomy- homologous strutures indicate common ancestry. Comparative embryology- similar embryo development across species. Molecular biology- DNA/protein simialries across species.
Smallest unit that can evolve
populations evolve because evolution involves changes in allele frequencies over generations.
Source of genetic variation
mutations random changes in DNA introduce new alleles. Sexual reproduction- shuffling of alleles occurs through crossing over and independent assortment. Reproductive rate- fast reproduction increases genetic variation.
Population’s
a group of interbreeding individuals in the same area. Species- a group that can interbreed and produce fertile offspring. Gene pool- all the alleles present in the population
Hardy-Weinberg theorem
if the population is not evolving, allele frequencies remain constant from gen to gen provided that no evolutionary forces act on it.
Consequences and conditions
if the population meet this expectation the population isn’t evolving. No mutations, random mating, no natural selection, lg pop size, no gene flow. all of these conditions are violated evolution happens.
Explain how genetic drift, gene flow, mutation, nonrandom mating and natural selection can cause microevolution.
genetic drift- random changes in allele frequencies within a population due to chance events
- gene flow- movement of alleles between populations through migrations of individuals or gametes, which can introduce new genetic material.
- mutation- random changes in DNA sequences that introduce new genetic variation
- nonrandom mating- preference fir certain triats can alter allele frequeinces. For example interbreeding.
- natural selection- differential survival and reproduction of idivuals based on their phenotypic traits. These more advantageous traits are more likely to survive and reproduce.
. Explain the role of population size in genetic drift (bottleneck effect and founder effect). Explain how allele frequency in a population is affected
- bottleneck effect- a drastic reduction in population size due to a catastrophic event. The surviving population has reduced genetic variation, and allele frequeinces.
- founder effect- when a small group of individual colonizes a new area, the new poplu has reduced genetic variation and different allele frequencies compared to the og.
- allele frequency impact- both bottleneck and founder effects can lead to reduced genetic diversity and changes in allele frequency affecting the poplu ability to adapt to environmental changes.
. Explain what is meant by the statement that natural selection is the only agent of microevolution that is adaptive.
natural selection is the only mechanism that consistently increases the frequency of advantageous alleles. Leading to adaptations that enhance survival and reproduction.
. Explain how genetic variation may be preserved in a natural population.
heterozygote advantage- they higher fitness and maintain both alleles in the poplu
- frequency-dependant selection- the fitness depends on its frequency to other phenotypes. Rare ones might have a advantage.
Diploidy- the presence of two chromosomes allows recessive alleles to be preserved in heterozygous.
Gene flow- new allele from other populations help maintain genetic diversity
- Recognize that selection acts on the phenotype and indirectly contributes to the overall fitness of a genotype.
- Natural selection acts on observable traits rather than directly on genotypes, since phenotypes are determined by genotypes, selection indirectly influences the overall fitness of genotypes.
- Differentiate between microevolution and macroevolution.
- Microevolution- refers to small-scale changes within a pop over time such as changes in allele frequencies due to genetic drift, gene flow, mutations, non-random mating, and natural selection.
- Macroevolution- involves large-scale changes that lead to new species. Events like speciation and extinction.
- Define biological species (E. Mayr) and list limitations to this concept
- a species is a group of indivuals that can interbreed and produce viable, fertile offspring in nature, are reproductively isolated from other such groups. Some liminations are asexual reproduction, fossil species, and hybridization.
- Explain how gene flow between closely related species can be prevented
- Reproductive isolation is the mechanism that prevents gene flow between closely related species maintaining boundaries.
- Distinguish between prezygotic and postzygotic isolating mechanisms
- Prezygotic isolating mechanisms- preventing mating or fertillzation between species.
- Temporal isolation- different mating seasons
- Behavioural isolation- diff mating behaviours
- Mechanical isolation- incompatible reproductive strutures
- Gametic isolation- sperm and egg cant fuse
- Habitat isolation- different habitats within same area.
Postzygotic isolating mechanisms- occurs after fertilization. - Reduced hybrid viability- fail to develop or die early
- Reduced hybrid fertility- offspring are inviable or sterile in subsequent generations
- Explain how hybrid breakdown maintains separate species even if fertilization occurs.
- Even if first-generation hybrids are viable and fertile, the gens beyond may show reduced fitness, preventing gene flow between species.
