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36 Cards in this Set
- Front
- Back
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Evolution |
Def: the idea that species change through time. change in allele frequencies in a population over time. |
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Theories |
Def: a supposition or a system of ideas intended to explain something, which is well tested and validated by extensive research.
The theory of evolution is a theory because it attempts to explain how organisms change through time. |
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Hypothesis |
Def: a supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation.
-must be falsifiable -can be refuted by single experiment |
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Typological thinking |
The concept that organisms of a species conform to a specific norm (unchanging). In this view variation is considered abnormal. |
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Lamarkian evolution |
-Individual phenotypes change in response to the environment (e.g. Giraffes get long neck through straining to eat food high up) -This phylogenetic trait is passed on to offspring, and this continues through the generation until Giraffes have longer necks. -Lemarkian evolution is progessive (i.e. organisms get better with time).
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Epigenetics |
Def: the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself (change in phenotype not a difference in nucleotide sequence). |
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Population |
Def: consists of individuals of the same species living in the same area at the same time.
Variations in the population exist |
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Population thinking |
Variation among individuals in a population is the key to understanding the nature of species.
Evolution by natural selection is all about change and diversity. |
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Revolutionary advances of Evolution |
1. Overturned the idea that species are static 2. Replaced typological thinking 3. Was scientific (i.e. could be tested by experiments, provided a mechanism for how things change) |
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Descent with modification |
Def: species today have descended from other, preexisting species and that species are modified, or change, through time.
-Modern species from ancestral species |
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Allele frequency |
Def: (or gene frequency), is the proportion of a particular allele (variant of a gene) among all allele copies being considered.
Formally def: the percentage of all alleles at a given locus in a population gene pool represented by a particular allele. |
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Allele |
Def: alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. |
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Fossil/Fossil Records |
-any trace of an organism that lived in the past.
Fossil records are organized by relative age because most fossils are found in sedimentary rocks (form in layers), so fossils from rocks underneath other rocks are judged to be older than those found above them. |
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Radioactive decay |
The steady rate at which unstable "parent" atoms are converted into more stable "daughter" atoms.
-Known for atoms like C-14 (unstable)-->C-12 (stable), and Uranium-238(or 235)-->Lead-206(or 207). |
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Extinct |
-when species are found to no longer exist after researchers realized that fossils of unknown species were not in unexplored areas of Earth. r
-indicates that species have gone extinct continuously through Earth's history, not just during catastrophic events. |
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Law of Succession |
-Extinct species are succeeded by similar species of the same region. |
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Transitional features |
fossil species with traits that are intermediate between those of older and younger species.
example: fossils have documented a gradual change over time from land-dwelling mammals that had limbs to ocean-dwelling mammals that had reduced or no limbs. |
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Vestigial traits |
Def: reduced or incompletely developed structure that has no function or reduced function, but is clearly similar to functioning organs or structure in closely related species.
Examples: Coccyx (tailbone) does not help with balance like a tail on a monkey, or Goosebumps that do not outwardly show emotional states like animals that "puff up" to seem more imposing. |
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Phylogenetic tree |
Def: (or evolutionary tree) is a branching diagram showing the inferred evolutionary relationships among various biological species based upon similarities and differences in their physical or genetic characteristics. |
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Homologies |
similarity that exists in species descended from a common ancestor. Studied at three levels.
Example: humans and dogs have hair because they share a common ancestor that was a mammal that also had hair. |
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Genetic Homology |
Def: the similarity in the DNA sequences of species. -the most fundamental level of homology.
Fun fact :except for one or two codons in a handful of species, the same 64 mRNA codons specify the same amino acids in all organisms studies. |
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Developmental Homology |
Def: similarity in embryonic traits. Observed through the overall morphology, or form, of embryos and in the fate of particular embryonic tissues. Example: early in development, structures called gill pouches and tails are formed in chicks, humans, and cats. later, gill pouches are lost in all three species, it became vestigial. |
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Structural Homology |
Def: developmental homologies are due to homologous genes that give rise to similarities in adult morphology.
Example: limbs of vertebrates. even though their function varies, all vertebrate limbs are modifications of the same number and arrangement of bones, due to a common ancestor that had limbs with the same basic plan. |
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Speciation |
Def: the formation of new and distinct species in the course of evolution. |
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Four Postulates |
1) the individual organisms that make up a population vary in the traits they possess, such as size and shape. 2) some of the trait differences are heritable, meaning can be passed onto offspring genetically, such as height. 3) in each generation, many more offspring are produced than can survive. only some individuals in a population survive long enough to produce offspring, and among those that produce offspring, some will produce more than others. 4) differential reproductive success: the subset of individuals that survive best and produce the most offspring is not a random sample of the population. Natural selection occurs when those with certain characteristics produce more offspring than those without the traits. |
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Fitness |
Def: ability of an individual to produce offspring, relative to that ability in other individuals in the population.
-measurable |
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Adaptation |
Def: heritable trait that increases the fitness of an individual in a particular environment relative to individuals lacking the trait.
-adaptation increases fitness |
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Evolution by Natural Selection |
-occurs when heritable variations lead to differential reproductive success. |
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Phenotype |
Def: observable traits of an individual
Examples: eye color, hair color, height |
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Genotype |
Def: alleles that underlie phenotypic traits.
Examples: The gene responsible for eye color, the gene responsible for hair color, the gene responsible for height. |
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Natural experiment |
Def: instead of comparing groups created by direct manipulation under controlled conditions, natural experiments allow researchers to compare treatment groups created by unplanned, natural changes in conditions. |
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What are some common misconceptions about natural selection? |
1) selection acts on individuals, but evolutionary change occurs in populations. 2) evolution is not goal-directed or progressive. adaptations do not occur because organisms want or need them. 3) animals do not do things for the good of the species. 4) not all traits are adaptive (ex: silent mutations in DNA sequences are extremely common, yet not adaptive). |
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Acclimitization |
Def: changes in an individual's phenotype that occur in response to changes in environmental conditions. -Gradual change -are not passed on to offspring. As a result, they cannot cause evolution.
Example: changes in your body as you get accustomed to living at higher elevation or in hot or cold environments. |
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Silent Mutation |
DNA mutations that do not significantly alter the phenotype of the organism in which they occur.
-can occur in non-coding regions (outside of genes within introns), or they may occur within exons. |
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Pleiotropy |
Def: one gene influences multiple, seemingly unrelated phenotypic traits.
Example: phenylketonuria, which is a human disease that affects multiple systems but is caused by one gene defect. |
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Fitness trade-off |
Def: a compromise between traits in terms of how they perform in the environment (ex: to grow or to defend). -because selection acts on many traits at once, every adaptation is a compromise. |
