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Topic 6: Mechanisms of Evolution
Terms in this set (72)
"The Origin of Species"
Many modern species are descendants of ancestral species, and the mechanism for this evolutionary process is natural selection. According to the theory of natural selection, a population can change over generations if individuals with certain heritable traits leave more offspring than others, resulting in evolutionary adaptation.
A process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are organisms with other characteristics.
Inherited characteristics of an organism that enhances its survival and reproduction in specific environments.
Descent with modifications; the idea that living species are descendants of ancestral species that were different from the present-day ones; also defined more narrowly as the change in genetic composition of a population from generation to generation.
A scientific discipline concerned with naming and classifying the diverse forms of life.
-(384-382 B.C.) Viewed species as fixed and concluded that life forms are arranged on a ladder of increasing complexity.
(1707-1778) A Swedish physician and botanist who sought to classify life's diversity. He developed the binomial system of naming species and he adopted a nested classification system.
(1769-1832) Developed paleontology. To explain the changes found in fossils over time, he advocated catastrophism (the principle that events in the past occurred suddenly and were caused by mechanisms different from those operating in the present.
(1797-1875) Developed uniformitarianism (mechanisms of organisms change over time). Proposed that the same geologic processes are operating today as on the past, and at the same rate.
(1744-1829) Developed the principle of use and disuse, the idea that parts of the body that are used become extensively larger and stronger, while those that are not used deteriorate, and the inheritance of acquired characteristics.
Contended that much of human suffering-disease, famine, and war-was the inescapable consequence of the human population's potential to increase faster than food supplies and other resources
(1726-1797) Proposed that Earth's geologic features could be explained by gradual mechanisms still operating.
Explains that the areas between strata show a devastating event which caused the extinction of animals in that area and then animals from surrounding areas populated it.
Attributes profound change to the cumulative product of slow but continuous change.
Voyage of the Beagle
Darwin was able to go on to the shore of South America and observe the various adaptations of plants and animals that inhabited diverse environments. After experiencing an earthquake in Chile he saw the earth raise a couple of feet revealing fossils high in the Andes Mountains. His stop at the Galapagos Islands allowed him to see the effects of geographic isolation on finches.
Darwin believed that whatever trait was most efficient in the success and reproduction of a species, then that species would adapt to acquire that trait. It is crucial to natural selection because some organisms must adapt to fit their environments.
Descent with modification
Darwin perceived unity in life, which he attributed to the descent of all organisms from an ancestor that lived in the remote past. He also thought that as the descendants of that ancestral organism lived in various habitats over millions of years, they had accumulated these diverse modifications, or adaptations that fit them to specific ways of life.
The concept allowed Darwin to reason that if artificial selection can achieve so much change in a short period of time, then natural selection should be capable of considerable modification of species over hundreds to thousands of generations. It put Darwin's natural selection into a shorter time frame.
Structures in different species that are similar because of common ancestry.
A structure of marginal, if any importance to an organism. They are historical remnants structures that had important functions in ancestors.
Having characteristics that are similar because of convergent evolution, not homology.
The geographic distribution of species. It is important to the study of evolution because it shows that species tend to be more closely related to other species from the same area than to other species with the same way of life but living in different areas
Evolutionary change below the species level; change in the allele frequencies in a population over generations.
A localized group of individuals that belong to the same biological species, capable of interbreeding and producing viable offspring.
The study of how populations change genetically over time.
The aggregate of all the alleles for all of the loci in all individuals in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population.
The theorem states that frequencies of alleles and genotypes will stay the same as long as the gametes are contributed to the next population at random. This appears to be a contradiction to evolution because it seems to say populations will never change. However, this condition only exists under certain conditions which do not apply to the majority of populations.
The reciprocal exchange of genetic material between nonsister chromatids during prophase one of meiosis; reshuffles alleles.
The random orientation of homologous pairs of chromosomes at metaphase of meiosis I. Each pair may either orient with either its maternal or paternal homolog, therefore increasing genetic variability.
The fusion of a male gamete with a female gamete during fertilization will make a zygote with many diploid combinations.
Unpredictable fluctuations in allele frequencies, reduces genetic variation over time through such losses of alleles.
When environmental change greatly reduces a population, the ratio of genes is mixed up. Certain alleles may be over/under-represented among the survivor. Usually occurs from a natural disaster.
Isolated individuals of a population establish a new population → limited gene pool.
Genetic additions and/or subtractions from a population resulting from the movement of gametes.
The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals
The contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus.
Gender reproductive success of heterozygous individuals compared to homozygote; it tends to preserve variation in gene pools. (ex.-heterozygous protection from the disease malaria in Africa)
Frequency dependent selection
It is when the fitness of any one morph declines if it becomes too common in the population. (ex.-if almost all red flowers declined in number, most insects would eat the white flowers, which would then become rare also)
Genetic diversity that confers no apparent selective advantage. Could stay recessive and dormant in genes; it would not effect selective advantage. (ex.-if my DNA was mutated, I might not know it)
Marked differences between the sexes in secondary sexual characteristics which are not directly associated with reproduction. (ex.-peacock feathers)
Selection "within the same sex" is a direct competition among individuals of one sex for mates of the opposite sex. (ex.-when rams buck heads to show the female that they are the stronger and more worthy of a mate than the loser)
Mate choice, individuals of one sex are choosy in selecting their mates from the other sex. (ex.-the female's choice depends on the showiness of the male's appearance or how they behave)
1. Evolution is limited by historical constraints. This means that a species cannot completely start fresh. New species are simply modifications of preexisting species.
2. Adaptations are often compromises. One adaptation may cause problems in certain aspects while also causing serious advantages (ex: a human is very flexible making it athletic, but humans, because of this, are very prone to torn ligaments and serious joint injuries).
3. Chance and natural selection interact.
4. Selection can only edit existing variations.
The origin of a new species in evolution.
Evolution on a scale of separated gene pools.
Evolutionary change below the species level; change in the allele.
Biological species concept
They define species as a population or group of populations whose members have the potential to interbreed in nature and produce fertile offspring but are unable to produce offspring with those in other populations. They are linked by who they can reproduce with.
(prezygotic barrier) Two populations occupy different habitats.
(prezygotic barrier) Two populations mate at different times of the day, month, season or year.
(prezygotic barrier) Sexual competition limits chance of mating.
(prezygotic barrier) Sex organs are incompatible.
(prezygotic barrier) Sperm cannot fertilize egg.
Reduced hybrid viability
(postzygotic barrier) Genes from parents interact and do not mix.
Reduced hybrid fertility
(postzygotic barrier) Chromosomes from parents do not match up and the offspring cannot reproduce.
(postzygotic barrier) Some first generation hybrids are fertile but cannot mate with original species.
Morphological species concept
Characterizes a species by its body shape, size, and other structural features. It applied to asexual and sexual organisms and can be useful without the information on gene flow.
Paleontological species concept
Focuses on morphologically discrete species known only from the fossil record. Many species are forced to be identified this way because there is little to know information on their mating abilities.
Ecological species concept
Views a species in terms of its ecological niche, its role in a biological community.
Phylogenetic species concept
Defines a species as a set of organisms with a unique genetic history; as one branch on the tree of life. Biologists trace the phylogenetic history of a species by comparing its physical characteristics or its molecular sequences with those of other organisms.
When gene flow is interrupted in a population and it is divided into geographically isolated subpopulations. Then one or both of the populations may undergo evolutionary change during the period of separation.
The development of new species in geographically overlapping populations. The speciation occurs when a mutation, or certain mating, occurs that creates genetic polymorphisms. It does not necessarily create phenotypic polymorphisms. After many generations, the polymorphism begins to create different organisms that look and act slightly differently than the original species, eventually creating a whole new species.
When an individual has more than two chromosome sets that came from a single species.
When two different species interbreed and combine their chromosomes, causing a polyploid.
Commonly occurs with plants due to the fact that they reproduce in vast amounts and occasionally interbreed.
Evolution of many diversely adapted species from common ancestor. Island chains are discussed with this topic because islands are areas where much allopatric speciation occurs. Many island species tend to float, fly, or blow over to seas to mainland or to different areas on the island. As one population gives rise to a new species and members of those species make their way to neighboring islands and so on. Many new species are formed with new characteristics enabling them to survive in different habitats. These places across island are still closely located, however, and some species make it back to the original species and they are able to coexist with their common ancestors because they still have similar traits.
Changes mostly as it buds from a parent species and then changes little for the rest of its existence. As the species diverge through the evolution sequence it is possible that a parent species could diverge and enter a stage of gradualism.
When species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations.
An evolutionary change in the rate or timing of developmental events.
It is the proportioning that helps give a body its specific form.
It is when reproductive development accelerates compared to somatic development; the sexually mature stage of a species may retain body features that were juvenile structures in an ancestral species.
They determine such basic features as where a pair of wings and a pair of legs will develop on a bird or how a plant's flowers parts are arranged.
These have had a great impact on vertebrates because they have introduced positional information to animal embryos.
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