Evolution Flashcards
Evolution
change in allele frequencies in a population
Microevolution vs. Macroevolution
changes in a single gene pool versus appearances of major evolutionary development or new species
Anagenesis or Phyletic Evolution
occurs when one species replaces another
Cladogenesis or Branching Evolution
occurs when a new species branches out from a parent species
Evidence for Evolution: The Fossil Record
Paleontology reveals the existence of species that have become extinct or have evolved into other species. Also, scientists discovered transitional forms that turn into modern animals. Radioactive aging and half-lives are used to age things.
Evidence for Evolution: Comparative Anatomy
Homologous, Vestigial and Analogous structures contribute to the understanding of anatomical structures and relationships.
Homologous Structures
Structures that share bone structure but vary in function. Ex. wing of bat, lateral fin of whale, and human arm
Analogous Structures
Structures that have the same function although the similarity is superficial. Ex. bat wings and fly wing
Vestigial Structures
Structures that do not sere a function although they are still around. Ex. pelvic bone of snake
Comparative Biochemistry
Organisms with a common ancestor have common biochemical pathways. The more closely related organisms are the more similar their biochemistry is. Explains testing on animals.
Comparative Embryology
Organisms with a common ancestors go through similar stages in their embryonic development, All vertebrate embryos go through stages in which they have gills.
Molecular Biology
All aerobic organisms contain cells that carry out aerobic respiration and contain the polypeptide cytochrome C. Comparing this polypeptide shows which organisms are most closely related.
Biogeography
Continental drift states that about 200 m.y.a. the continents were locked into Pangea that separated 150 m.y.a.. Studying geographic distribution of living organisms and fossils confirms the continental first theory.
Aristotle - 1
The Scala Nature stated that all life forms can be arranged on a ladder of increasing complexity each with their own rung of which humans are at the top. The species are permanent and do not evolve.
Carolus Linnaeus - 2
Specialized in taxonomy and named/classified organisms. He developed the naming system called the binomial nomenclature. In this system every organisms has a name consisting of a genus and species.
Cuvier - 3
Studied fossils and realized that each stratum of Earth is characterized by different fossils. He believed that a series of catastrophes were responsible for the changes in the organisms on Earth. He oppose evolution.
James Hutton - 4
The theory of gradualism stated that Earth had been molded by gradual changes not violent, quick ones. The effects of wind, weather and geologic changes were those that creating canyons and ranges. His theory came from the idea that the Earth had a long history.
Lyell - 5
Geologist that stated that geological changes result from slow, continuous actions. He believed the Earth was older than 6,000 years.
Lamarck - 5
Contemporary of Darwin who developed theories of evolution. His theory relies on the ideas of inheritance of acquired characteristics and use and disuse. He stated that individual organisms change in response in their environment.
Wallace - 6
A naturalist author that discussed the idea of natural selection, identical to Darwin.
Darwin - 7
Naturalist and author that worked out the theory of natural selection and descent with modification as the mechanism for how populations evolve. On the Origin of Species was published about his work.
Darwin’s Theory of Natural Selection
- Populations grow exponentially and overpopulate to deplete resources.
- Overpopulation results in competition and a struggle for existence.
- In any population there is variation and an unequal ability of individuals to survive and reproduce.
- Only best-fit individuals survive and get to pass on their traits
- Evolution occurs as advantageous traits accumulate in the population.
How insects become resistant?
Some insects are resistant to a particular chemical insecticide and have a selective advantage. Over time, the proportion of individuals with longer necks increase.
Five Types of Selection
stabilizing, diversifying, directional, sexual, and artificial
Stabilizing Selection
Eliminates the extremes and favors the more common immediate forms. In humans birth weight in the 6-8 pound range. In starlings, birds with 5 eggs have more young survive than birds with more.
Disruptive/Diversifying Selection
Increases the extreme types in a population at the expense of the intermediate forms. Results in balanced polymorphism.
Balanced Polymorphism
one population is divided into two distinct types; over a great length of time this may result in the formation of two new species
Directional Selection
one phenotype replaces another in the gene pool
Directional Selection: Peppered Moths
Until 1845, most peppered moths were light and few were dark. Due to the pollution in the industrial regions dark color frequency increased because they could camouflage better.
Directional Selection: Antibiotics
Bacteria appeared that were resistant to antibiotics and are transferred through plasmids which can spread and cause antibiotic resistance.
Sexual Selection
Selection based on secondary sexual characteristics related to competing for and attracting mates.
Sexual Dimorphism
difference in appearance between males and females
Artificial Selection
Humans breed plants and animals with desired traits as breeding stock.
Balanced Polymorphism
The presence of two or more phenotypically distinct forms of a trait in a single population of a species. Each morph is better adapted in a different area but both varieties continue to exist.
Geographic Variation
Two different varieties of rabbit continue to exist in two different regions. Rabbits living in the northern snow have white coats and short ears to conserve heat. Rabbits in the southern heat have mottled fur and long ears. This is the north-south cline.
Cline
graded variation in the phenotype of an organism
Sexual Reproduction
Provides variation due to the shuffling and recombination of alleles during meiosis and fertilization.
Independent Assortment of Chromosomes
during metaphase I, this results in recombination of unlinked genes
Crossing-Over
the exchange of homologous chromosomes and occurs during meiosis I; it produces individual chromosomes combine genes inherited from two parents; in humans 2 or 3 events occur
Random Fertilization
one ovum by one sperm out of millions results in enormous variety among the offspring
Outbreeding
mating of organisms within one species that are not closely related; maintains variation within a species and a strong gene pool; inbreeding causes detrimental recessive traits to build up
Diploidy
the 2n condition maintains/shelters a hidden pool of alleles that may not be suitable under the present conditions but that could be advantageous when conditions change in the future
Heterozygous Advantage
phenomenon in which a hybrid individual is selected for because it has better reproductive success ; this maintains multiple alleles in a population; ex. Sickle Cell Anemia in the West Nile
Frequency-Dependent Selection or the Minority Advantage
decreases the frequency of more common phenotypes and increases the frequency of the less common ones; ex. search image
Search Image
A standard representation of prey that predators have in their mind. The most common type will be preyed upon disproportionately while the less common individuals will be preyed upon less.
Evolutionary Neutral Traits
Traits that seem to have no selective value. Examples are blood type and fingerprint variation.
Causes of Evolution: Genetic Drift
A change in the gene pool due to chance. It is a fluctuation in frequency of alleles from one generation to another that is unpredictable.
Genetic Drift: Bottleneck Effect
Natural disasters such as fire, earthquake, and flood reduce the size of a population unselectively resulting in the loss of genetic variation. The resulting population is much smaller and not representative of the original one. Ex. Tay-Sachs disease among Eastern European Jews by Jews in the Middle Ages.
Genetic Drift: The Founder Effect
When a small population breaks away from a larger one to colonize a new area, it is most likely not genetically representative of the original larger population. Rare alleles can be overrepresented. Ex. polydactyly in the Old Order of Amish of Lancaster.
Gene Flow
The movement of alleles into or out of a population. It can occur as a result of the migration of fertile individuals or gametes between populations. Ex. pollen
Mutations
Changes in genetic material and are the raw material for evolutionary change. They increase diversity. A single point mutation can introduce a new allele into a population.
Nonrandom Mating
Individuals choose their mates for a specific reason. The selection of a mate serves to eliminate the less-fit individuals.
Natural Selection
Individuals who are better adapted to a particular environment exhibit better reproductive success. They have more offspring to survive and pass their genes on to more offspring.
Stabilizing Factors of Hardy-Weinberg Equilibrium
- The population must be very large.
- The population must be isolated from other populations.
- There must be no mutations in the population.
- Mating must be random.
- No natural selection.
Hardy-Weinberg Equation
Enables us to calculate frequencies of alleles in a population. - p^2 + 2pq + q^2 = 1 - and - p + q = 1. P represents the dominant allele and q represents the recessive allele.
Species
population whose members have the potential to interbreed in nature and provide viable, fertile offspring
Reproductive Isolation
Terms by which a species in defined. One group of genes becomes isolated from another and begin a separate evolutionary history. Once separated and with enough time they may become two different species.
Speciation
anything that fragments a population and isolates small groups of individuals may cause this
Allopatric Speciation
caused by geographic isolation (separation by mountain ranges, canyons, rivers, lakes, glaciers, altitude or longitude)
Sympatric Speciation
no caused by geographic isolation; polyploidy, habitat isolation, behavioral isolation, temporal isolation, and reproductive isolation
Polyploidy
condition where a cell has more than two complete sets of chromosomes; it can occur through breeding or naturally; nondisjunction can cause this; plants that are polyploidy cannot breed with those that are not polyploidy
Habitat Isolation
two organisms live in the same area but rarely encounter each other; ex, one snake in water the other on land
Behavioral Isolation
Elaborate mating rituals can be disturbed. For example, Sticklebacks are small salt water fish that change color and develop a red underbelly in response to sunlight. This starts a dance that does not occur if these steps are interrupted.
Temporal Isolation
Temporal refers to time. A flowering plant colonizes a region with areas that are warm and sunny and areas that are cold and shady. The flower becomes sexually mature at different times.
Reproductive Isolation
Prezygotic and postzygotic barriers; Differences in the structure of genitalia and difference in flower shape which prevent fertilization.
Prezygotic Barrier
Things that prevent mating. Ex. a small male dog and a large female dog
Postzygotic Barrier
Things that prevent production of fertile offspring once mating occurs. Ex. nonviable zygote.
Divergent Evolution
A population becomes isolated from the rest of the species, becomes exposed to new selective pressures and evolves into a new species. Allopatric and sympatric isolations.
Convergent Evolution
An unrelated species occupy the same environment and are subject to the same selective pressures and show similar adaptations. Ex. the whale’s appearance which matches the fish
Parallel Evolution
Describes two related species that have made similar evolutionary adaptations after their divergence from a common ancestor. Ex. marsupial mammals of Australia and the placental mammals of North America
Coevolution
The reciprocal evolutionary set of adaptations of two interacting species. All predator-prey relationships are examples and the relationship between the monarch butterfly and the milkweed plant is another.
Adaptive Radiation
The emergence of numerous species from a common ancestor introduced into an environment. Each newly emerging form specializes to fill an ecological niche.
Gradualism
The theory that organisms descend form a common ancestor gradually, over a long period of time, in a linear or branching fashion. According to this theory, fossils exist as evidence of every stage in the evolution of every species with no missing links. The fossil record is at odds because they rarely find transitional forms or missing links.
Punctuated Equilibrium: Stephen J. Gould and Niles Eldridge
Proposed that new species appear suddenly after long periods of stasis. A new species changes most as it buds from a parent species then changes little for the rest of its existence.
Allopatric Model
A new species arises in a different place and expands its range, outcompeting and replacing the ancestral species.
Ancient Atmosphere
CH4, NH3, CO, Co2, N2 and H2O were abundant but there was no free O2. There was intense lightening and ultraviolet radiation that penetrated the primitive atmosphere, providing energy for chemical reactions.
A. I. Oparin and J. B. S. Haldane
In the 1920s, hypothesize separately that under the conditions of early Earth, organic molecules could form. Without corrosively reactive molecular oxygen present to react with and degrade them, organic molecules could form and remain.
Stanley Miller and Harold Urey
In the 1950s, tested (using electricity to mimic lightening and UV light) the Oparin-Haldane hypothesized and proved that almost any energy source would have converted the molecules in the early atmosphere to organic molecules like amino acids.
Sidney Fox
In recent years, carried out experiences similar to Miller and Urey. He was able to produce membrane bound, cell-like structures he called proteinoid microspheres.
First Cells on Earth
3.5 m.y.a. ;anerobic heterotrophic prokaryotes; absorbed organic molecules from the surrounding primordial soup to use a nutrient sources
Endosymbiotic Theory
Mitochondria and Chloroplasts were one free living prokaryotes that took residence in other prokaryotes (phagocytosis) ; this mutualistic relationship worked so well that it became permanent
Evidence of Endosymbiosis for Mitochondria and Chloroplasts
- have their own DNA
- DNY is more like prokaryotic DNA than eukaryotic DNA as it is not wrapped with histones
- Organelles have double membranes: the inner belong to the host plasma membrane
