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AP Bio Mod 40-50
| Question | Answer |
|---|---|
| Stabilizing Selection | Selection that favors intermediate traits and reduces extremes. |
| Directional Selection | Selection that favors one extreme phenotype. |
| Disruptive Selection () | Selection that favors both extremes of a trait while selecting against the average. -most likely to cause speciation or formation of different groups in a species |
| Convergent Evolution | Unrelated species evolve similar traits because they face similar environmental pressures (not common ancestors) -Ex: Sharks (fish) and dolphins (mammals) both evolved streamlined bodies for swimming. |
| Divergent Evolution | -Related species evolve different traits as they adapt to different environments. Ex:whales, and humans all share a common ancestor, but their forelimbs evolved into different structures arms=humans flippers=whales |
| Artificial Selection | Human direct breeding to enhance desired traits in organisms |
| Sexual selection | -A type of natural selection where traits evolve because they increase an individual’s chances of attracting a mate -Ex:Male peacocks have large, colorful tails that attract females |
| Homology / Homologous Structures | Structures with similar anatomy due to common ancestry but possibly different functions Ex: human arm and whale flipper). |
| Vestigial Organs | Structures that have little or no current function but were functional in ancestors Ex: human appendix). |
| Heterozygote advantage | A situation in which carriers of a recessive trait have the greatest chance for survival and reproduction -Ex: Those who are sickle cell carriers can survive malaria and sickle cell |
| Gradualism speciation | -a type of speciatiom of speciation in which new species arise by a slow, steady accumulation of changes |
| Bottleneck effect | - when a Catastrophic event leaves only a few survivors, altering the gene pool and making population size smaller |
| Genetic drift | Random fluctuation in allele frequency due to small population size - Two Causes: Bottleneck effect and Founder effect |
| Founder Effect | -when a small group colonizes a new area and carries only part of the original gene pool. |
| Hox genes | Genes controlling the body plan and developmental fate of cells |
| Punctuated equilibrium | Rapid evolutionary change followed by long periods of little change |
| Sympatric speciation | New species forms within the same population due to reproductive barriers |
| Hardy-Weinberg Equilibrium | -A model describing a population where allele frequencies remain constant because no evolution occurs. -populations are in Equilibrium if allele frequencies are constant in each generation |
| Microevolution | Small changes in allele frequencies within a population over time |
| Macroevolution | Large-scale evolutionary changes that occur over long periods of time, often resulting in the formation of new species or major groups. -Ex:The evolution of whales from land-dwelling mammals. |
| Sexual Dimorphism | Differences in physical traits between males and females of the same species (ex. peacock tail). |
| analogous traits | traits that are similar due to convergent evolution |
| Molecular Clock | A method that uses the rate of DNA mutations to estimate how long ago two species diverged. Ex: Comparing DNA differences between humans and chimpanzees to estimate when they split. |
| Conserved Traits | Traits that have changed very little over time because they are essential for survival. Often used to justify common ancestry Ex: DNA sequences involved in basic cell functions. |
| Radioactive Dating | A technique that determines the age of fossils or rocks using the decay of radioactive isotopes. Example: Carbon-14 dating used on once-living materials. |
| Endemic Species | Species that are found only in one specific geographic area. Example: Lemurs only in Madagascar. |
| Invasive Species | -Non-native species that spread rapidly and harm native ecosystems |
| Gene flow | a chnage in the frequncy of traits in a poplation due to immigration |
| Allopatric speciation | -speciation that occurs due to physical barriers between groups in a population -with enough time and evolution, the two groups become reproductively isolated |
| Hybrid Zone | A geographic area where two different species meet and interbreed, producing hybrids. -these hybrids keeps the species connected Ex: Two bird species overlapping and producing mixed offspring. |
| Hybridization | – The process of mating between two different species to produce hybrid offspring. Ex: A horse and donkey mating to produce a mule. |
| Hybrid Population | A group of organisms made up of hybrid individuals resulting from repeated hybridization. |
| Reinforcement | Natural selection increases reproductive isolation by favoring traits that prevent hybridization -occurs because hybrids are less fit Ex: Two species evolve different mating calls to avoid producing weak hybrids. |
| Stability | -Hybrids continue to be produced and persist over time without increased isolation. -Ex: Hybrid offspring survive and reproduce, maintaining the hybrid zone. |
| Prezygotic Barriers | Reproductive barriers that prevent mating or fertilization (ex. different mating seasons). -Types:Temporal, Habitat, Behavioral, Mechanical, and Gametic Isolation |
| Temporal Isolation | Temporal Isolation – Species breed at different times or seasons. Example: One frog species breeds in spring, another in summer. |
| Habitat Isolation | Species live in different habitats and rarely meet. Example: One insect lives on oak trees, another on pine trees. |
| Behavioral Isolation | Different species have distinct courtship behaviors. Example: Male fireflies use unique light patterns to attract mates of their species. |
| Mechanical Isolation | Physical differences prevent mating. Example: Flowers’ shapes only allow pollination by certain insects; genitalia of animals may not fit together. |
| Postzygotic Barriers | Reproductive barriers that act after fertilization, reducing the fitness of hybrids. Types: Reduced Hybrid Viability, Reduced Hybrid Fertility, and Hybrid Breakdown |
| Reduced Hybrid Viability | Hybrids fail to develop properly or die early. Example: Salamander hybrids die before reaching adulthood. |
| Reduced Hybrid Fertility | Hybrids are sterile and cannot reproduce. Example: Mule (horse × donkey) cannot produce offspring. |
| Hybrid Breakdown | Hybrids can reproduce, but future generations following the hybrids are weak or sterile. Example: Certain hybrid crops produce sterile or weak second-generation plants. |
| Biological Species Concept | -Defines species as a group of organisms that can interbreed and produce fertile offspring - Example: Horses and donkeys are different species because their offspring (mules) are sterile. |
| Ecological Species Concept | -A species is a group of organisms that occupy the same ecological niche (role and environment) -Ex: Two closely related lizard species in the same forest might be different species because one lives in trees and the other on the ground. |
| Morphospecies Concept | -A species is defined by distinct physical traits or morphology. |
| Phylogenetic Species Concept | -say that a species is the smallest group of organisms that share a common ancestor, forming a distinct branch on a phylogenetic tree. -Ex: Genetic analysis shows all modern humans form a single branch, separate from Neanderthals. |
| Polyploidy | -Polyploidy occurs when an organism has more than two complete sets of chromosomes -Two types:Autopolyploidy and Allopolyploidy |
| Autopolyploidy | -Chromosome duplication within a single species. -Ex: A 2n plant produces 4n offspring that can’t breed with 2n parent plants → new species forms. |
| Allopolyploidy | Chromosome sets come from hybridization between two species, followed by chromosome doubling. Ex: Wheat is a allopolyploid that is formed from the hybridization of three grass species. |
| Characters | -Traits or features of an organism used to compare species and determine evolutionary relationships. -Can be morphological, molecular, or behavioral. -Ex: Number of limbs, presence of feathers, DNA sequence. |
| Synapomorphies/ Shared Characters | -A derived character shared by two or more species that originated in their most recent common ancestor. -Ex: Mammary glands are a synapomorphy of all mammalsderived from a common mammalian ancestor. |
| Derived Character | -A trait that evolved in a lineage after it diverged from its common ancestor, distinguishing that group from its ancestors. -Ex: Feathers in birds—they are a derived trait compared to their dinosaur ancestors. |
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KenechukwuIE