Biology Chapter 15 and 16 (evolution and gene variation) – Flashcards
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evolution
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the process by which modern organisms have descended from ancient organsims
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scientific theory
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a well-supported testable explanation of phenomena that have occurred in the natural world
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What did Charles Darwin contribute to science?
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During his travels he made numerous observations and collected evidence that led him to propose a hypothesis about the way life changes over time.
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Who wrote the book in 1859 "Origin of Species"?
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Charles Darwin
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fossils
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preserved remains of ancient organisms
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artificial selection
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nature provided the variation and humans selected those variations that they found useful
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struggle for existence
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members of each species compete regularly to obtain food, living space, and other necessities of life
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fitness
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the ability of an individual to survive and reproduce in its specific environment
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adaptation
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any inherited characteristic that increases and organism's chance of survival
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survival of the fittest
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individuals that are better suited to their environment survive and reproduce most successfully
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natural selection
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only certain individuals of a population produce new individuals; affects which individuals survive and reproduce and which do not.
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How does natural selection affect polygenic traits?
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it can affect the distributions of phenotypes in any of three ways. 1. Directional selection 2. Stabilizing selection 3. disruptive selection
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descent with modification
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each living species has descended, with changes, from other species over time
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common descent
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all species-living and extinct-were derived from common ancestors
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homologous structures
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structures that have different mature forms but develop from the same embryonic tissues
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vestigial organs
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organs of many animals are so reduced in size that they are just traces of homologous organs in other species
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population
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a group of individuals of the same species that interbreed
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gene pool
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consists of all genes, including all the different alleles, that are present in a population
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relative frequency of an allele
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the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur; expressed in PERCENTAGES
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evolution in genetic terms
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any change in the relative frequency in a population
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two main sources of genetic (heritable) variation
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mutations and genetic shuffling that results from sexual reproduction
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mutation
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any change in a sequence of DNA
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gene shuffling
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occurs during production of gametes (meiosis / sexual reproduction). usually by messing up the crossing over
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single-gene trait
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controlled by a single gene that has two alleles. leads to two distinct phenotypes
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polygenic trait
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controlled by two or more genes. often has two or more alleles
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bell-shaped curve
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aka normal distribution. is typical polygenic traits
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how can natural selection lead to evolution?
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natural selection on single-gene traits can lead to changes in allele frequencies and thus to evolution
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directional selection
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when individuals at one end of the curve have higher frequencies than individuals at the middle or other end (beak size on birds)
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stabilizing selection
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when individuals near the center of the curve have higher fitness than individuals at either end of the curve (birth weight of human babies)
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disruptive selection
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when individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle (beak size where small and large seeds are common, but medium seeds are not)
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genetic drift
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random change in allele frequency. usually in small populations
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founder effect
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a situation in which allele frequencies change as a result of the migration of a small subgroup of a population
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hardy-weinberg principle
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states that allele grequencies in a population will remain constant unless one or more factors cause those frequencies to change
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genetic equilibrium
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the situation in which allele frequencies remain constant
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five conditions required to maintain genetic equilibrium
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1) must be random mating 2) population must be very large 3) there can be no movement into or out of the population 4) no mutations 5) no natural selection
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random mating
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ensures that each individual has an equal chance of passing on its alleles to its offspring
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large population
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genetic drift has less effect on large populations
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no movement into/out of population
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individuals may bring new alleles into our out of population. the population's gene pool must be kept separate from the gene pools of other populations
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no mutations
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if genes mutate from one form into another, new alleles may be introduced into the population and allele frequencies will change
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no natural selection
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all genotypes in the population must have equal probabilities of survival and reproduction
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speciation
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formation of new species
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reproductive isolation
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is when the members of two populations cannot interbreed and produce fertile offspring
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behavioral isolationism
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when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior
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geographic isolation
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when two populations are separated by geographic barriers such as rivers, mountains, etc
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temporal isolation
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when two or more species reproduce at different times. occurs mainly in plants
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order in which speciation occurs
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1) founding of a new population 2) geographic isolation (some moved islands) 3) changes in the new population's gene pool (adapted) 4) reproductive isolation (preferred mating with so and so) 5) ecological competition 6) continued evolution
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Peter and Rosemary Grant
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conducted 30 year experiment on galapagos' finches in daphne major. collected data on finches. found that beak size of living bird fluctuated with seasons and food supply (natural selection)
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Who proposed a mechanism for evolution called natural selection?
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Charles Darwin
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Who noted that plant and animal breeders would breed only largest hogs, the fastest horses, or the cow that proudced the most milk (artifical selection)
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Charles Darwin
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What happens to individuals with characteristics that are not well suited to their environment?
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they either die or leave few offspring (survival of the fittest)
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Who is known for survival of the fittest?
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Charles Darwin
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James Hutton
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He estimates the Earth to be millions - not thousands - of years old.
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Thomas Malthus
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Wrote the essay "Principle of Population" on population growth theory
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Thomas Malthus
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He predicted that the human population will grow faster than the space and food supplies needed to sustain it. aka population growth
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Jean-Baptiste Lamarck
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is known for his theory of inheritance of acquired traits. The theory was flawed but he was also the first to propose a mechanism explaining how organisms change over time.
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Charles Lyell
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wrote the book "Principles of Geology" - explaining that processes occurring now have shaped Earth's geological features over long periods of time.
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Alfred Wallace
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This man wrote to Darwin speculating on evolution by natural selection, based on his studies of the distribution of plants and animals.
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bell shaped curve AKA (also known as)
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normal distribution
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allele
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different types of genes
