Ch. 11 Evolution Flashcards
Microevolution
the changes in a single gene pool
Macroevolution
the appearance of a major evolutionary development or a new species.
Speciation can occur in two ways.
Anagenesis or phyletic evolution : once species replaces another.
Cladogenesis or branching evolution: when a new species branches out from a parent species.
Evidence for evolution : six areas
- fossil record
- comparative anatomy
- comparative biochemistry
- Comparative embryology
5 Molecular biology - Biogeoraphy
Evidence for evolution: 1. Fossil record
radioactive dating and half-life indicate that the earth is about 4.6 billion years old. Prokaryotes were the first organisms to develop on earth and they are the oldest fossils.
Comparative anatomy - Homologous structures
Have a common origin and reflect a common ancestry. The wing of a bat, the lateral fin of a whale, and the human arm all have the same internal bone structure, although the function of each varies.
Comparative anatomy - Analogous stuctures
such as a bat’s wing and a fly’s wing have the same function. However, the similarity is superficial and reflects an adaptation to similar environments, not descent from a recent common ancestor
Comparative anatomy - Vestigial(남아있는) structures
such as the appendix are evidence that structures have evolved. The appendix is a vestige of a structure needed when human ancestors ate a very different diet.
Comparative biochemistry
The more closely related the organisms are to each other, the more similar their biochemistry is. Humans and mice are both mammals. This close relationship is the reason that medical researchers can test new medicines on mice and extrapolate the results to humans.
Comparative Embryology
Closely related organisms go through similar stages in their embryonic development. ex) all vertebrate embryos go through a stage in which they have gill pouches on the sides of their throats. In fish, the gill pouches develop into gills. In mammals, they develop into eustachian tubes in the ears.
Molecular biology
Since all aerobic organisms contain cells that carry out aerobic cell respiration, they all contain the polypeptide cytochrome c. A comparison o the amino acid sequence of cytochrome c among different organisms shows which organisms are most closely related. The cytochrome c in human cells is almost identical to that of our closest relatives the chimpanzee and gorilla but differs from that of a pig.
Biogeography
The theory of continental drift states that about 200 million years ago, the continents were locked together in a single supercontinent called Pangea. which slowly separated into seven continents over the course of 150 million years. study of the location of marsupial fossils and the geographic distribution of living marsupial s which is limited almost exclusively to Australia, confirms this theory.
Historical context for evolutionary theory
Aristotle spoke for the Ancient world with his Scala Natura: all life-forms can be arranged on a ladder of increasing complexity, each with its own allotted rung. the species are permanent and do not evolve. Humans are at the pinnacle of this ladder of increasing complexity.
Carolus Linnaeus or Carl von Linne
Specialized in taxonomy, the branch of biology( naming and classifying the diverse forms of life). He believed that scientists should study life and that a classification system would reveal a divine plan.
The naming system used today: binomial nomenclature.
-Genus name and a species name. the scientific name of humans is Homo sapiens.
Cuvier
studied fossils and realized that each stratum(지층) of earth is characterized by different fossils. He believed that a series of catastrophes(재앙) was responsible for the changes in the organisms on earth and was a strong opponent of evolution.
James Hutton
Theory of gradualism. Stated that the earth had been molded not by sudden, violent events but by slow gradual change. the effects of wind, weather, and the flow of water formed the various geologic features on earth, such as mountain ranges and canyons.
Lyell
stated that geological change results from slow, continuous actions.
Lamarck
a contemporary of Darwin who also developed a theory of evolution. His theory relies on the ideas of inheritance of acquired characteristics and use and disuse. Individual organisms change in response to their environment. ex) Giraffe developed a long neck because it ate leaves of the tall acacia tree for nourishment and had to stretch to reach them. This may seem funny today, it was accepted in the early 19th century.
Wallace
essay discussing the process of natural selection identical to Darwin’s. which had not yet been published.
Darwin
Theory of natural selection or descent with modification as the mechanism for how populations evolve, but he did not publish them. Perhaps he was afraid of the furor(열광적칭찬) his theories would cause. He finally published “on the origin of the species”
Darwin’s theory of natural selection
- Populations tend to grow exponentially, over populate, and exceed their 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. Darwin however could not explain the origin of variation in a population. (Mendel’s theory of genetics published after natural selection. )
- Only the best-fit individuals survive and get to pass on their traits to offspring.
- Evolution occurs as advantageous traits accumulate in a population. - No individual organism changes in response to pressure from the environment. The frequency of an allele within a population changes.
How the giraffe got its long neck
According to Darwin’s theory, ancestral giraffes were short-necked animals. (neck length varied) As the population competing for the limited food supply increased, the taller individuals had a better change of surviving than those with shorter necks. over time, the proportion of giraffes in the population with longer necks increased until only long- necked giraffes existed.
How insects “become” resistant to pesticides
Insects do not actually become resistant to pesticides. (농약). instead, some insects are resistant to a particular chemical insecticide. when the environment is sprayed with that insecticide, the resistant insects have the selective advantage. All the insects not resistant to the insecticide die, and the remaining resistant ones breed quickly with no competition. The entirely new population is resistant to the insecticide. Insecticide resistance is just an example of directional selection.
Types of selection: 1. Stabilizing selection
Stabilizing selection eliminates the extremes and favors the more common intermediate forms. Many mutant(돌연변이) forms are weeded out in this way.
ex) humans: Babies weigh 6-8 pounds. babies much smaller and much larger, infant mortality is greater.
Swiss starlings: genotypes that lead to a clutch size ( the number of eggs a bird lays) of up to five will have more surviving young than birds of the same species that lay a larger or smaller number of eggs.
- Disruptive(분열성) or diversifying(다양성) selection
Increases the extreme types in a population at the expense of intermediate forms. Balanced polymorphism- one population divided into two distinct types. over great length of time, disruptive selection may result in the formation of two new species.
- Directional selection
Changing environmental conditions. One phenotype replaces another in the gene pool.
ex 1) industrial melanism in peppered moths. - increasing industrialization, smoke, making all plants and rocks dark. Moths were light before industrialization, but after, they are dark. Dark moths were camouflaged in their environment and had the selective advantage.
ex2) Produce rapid shifts in allelic frequencies. - after discovery of antibiotics, bacteria appeared that were resistant to these drugs. The genes for antibiotic resistance are carried on plasmids, small DNA molecules, which can be transferred from one bacterial cell to another and which can spread the mutation for antibiotic resistance very rapidly. Since only resistant individuals survive to reproduce, the next generation will all be resistant.
- Sexual selection
Based on variation in secondary sexual characteristics related to competing for and attracting mates.
In males, the evolution of horns antlers, large stature and great strength. Differences in appearance between males and females - sexual dimorphism.
In many species of birds, the females are colored in a way to blend in to protect them and their young.
- Artificial selection
Humans breed plants and animals by seeking individuals with desired traits as breeding stock.
Ex) racehorses are bred for speed.
Sources of Variation in a population - 1. Balanced Polymorphism
the presence of two or more phenotypically distinct forms of a trait in a single population of a species. Each morph ( 형태, 변종) is better adapted in a different area but both varieties continue to exist.
- Geographic Variation - cline
two different varieties of rabbit continue to exist in two different regions in North america. Rabbits in the cold have short ears to conserve body heat. Rabbits in warmer, have mottled fur to blend in with surrounding woodsy areas and long ears to radiate off excess body heat.
-> The variation in rabbit appearance is due to differences in northern and southern environments: North-south cline.
Cline - a graded variation in the phenotype of an organism
- Sexual reproduction
variation due to the shuffling and recombination of alleles during meiosis and fertilization.
- Independent assortment of chromosomes. Metaphase I
- Crossing- over : meiosis I
- Random fertilization : one ovum by one sperm out of millions results in variety among the offspring.
3. Human embryos have tails
Comparative embrology
7 The wing of the bat and a human’s arm have different functions and appear very different. Yet, the underlying anatomy is basically the same. Therefore, these structures are examples of
Homology
- Homologous structures demonstrate a common ancestry. They may not look alike, but they have an underlying common structure. Analogous structures may have the same function and look alike but they do not have a common structure nor do they have a common ancestry.
9 According to the Hardy-Winberg equation, the dominant trait is represented by
P
10 The population of peppered moths in England changed from white to black in fifty years.
Directional selection - The black peppered moths replaced the white peppered moths. Since one characteristic replaced another, this is directional selection.
13 In one region of New Jersey there exist two distinct types of one species of snake
Disruptive selection - Disruptive selection tends to select for the extremes. Originally, there was probably a range of coloration of snakes in the area in question. Over time, pressure from the environment selected against different colorations until only two remained.
16 Cline example
In one species of rabbit, the ones that evolved in the cold, snowy north are white, while the ones that evolved in the south are brown. - A cline is a change in some trait along some geographic axis, such as a north south cline. In this example, the animal is camouflaged by its colorings.
17 Who synthesized proteinoid microspheres in the laboratory using an apparatus that mimicked the early earth?
Fox- Sidney fox was able to produce these cell-like structures, which he called proteinoid microspheres, when he began with amino acids in his experiment.
19 which part of the theory of evolution did Darwin develop after reading Thomas Malthus?
Populations tend to grow exponentially, overpopulate and exceed their resources. - Malthus was a mathematician studying populations. He stated that populations tend to overpopulation and exceed their resources. this leads to starvation, disease and death.
20 In a population of 1000 people, 90 have blue eyes. What percent of the population has hybrid brown eyes?
42% - Of the total population, 9% have blue eyes (90 out of 1000) so 9^2= 0.09 and q=0.3. Therefore, p=0.7 and the frequency of hybrid brown = 2pq = 42%
22. Darwin’s finches
Adaptive radiation- is the emergence (출현) of numerous species from one common ancestor introduced into a new environment. Today, 13 different species of finches are on the Galapagos Islands where originally there was only 1 species. Each species fills a different niche(생태적 지위).
23 The establishment of a genetically unique population through genetic drift
Founder effect - genetic drift is evolution through chance. The founder effect is one example of genetic drift. Another is the bottleneck effect.
24 The independent development of similarities between unrelated groups resulting from adaptation to similar environments
Convergent evolution - ex) whale and shark. The two animals are unrelated. The wale is a mammal and the shark is a fish. however, they look alike because they experience the same environmental pressures. They both have a streamlined appearance with fins because that design is best for living in the ocean, not because they are related or have a recent common ancestor.
Allopatric Speciation
caused by geographic isolation: separation by mountain ranges, canyons, rivers, lakes, glaciers, altitude or longitude
Sympatric Speciation
Polyploidy, habitat isolation, behavioral isolation, temporal isolation, and reproductive isolation.
Divergent evolution
occurs when a population becomes isolated (for any reason) from the rest of the species, becomes exposed to new selective pressures, and evolves into a new species. ex) Allopatric and sympatric speciation.
Convergent evolution
When unrelated speies occupy the same environment, they are subjected to similar selective pressures and show similar adaptations. ex) whale and shark
Parallel evolution
Two related species that have made similar evolutionary adaptations in similar environments after their divergence from a common ancestor. ex) Marsupial mammals and the placental mammals.
Coevolution
Reciprocal evolutionary set of adaptations of two interacting species. All predator - prey relationships are examples and the relationship between the monarch butterfly and milkweed plant is another. The milkweed plant contains poisons that deter herbivores from eating them. The butterfly lays its eggs in the milkweed plant and when the larvae (caterpillars) hatch they feed on the milk.
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. All 14 species of Darwin’s finches that live on the Galapagos Islands today diverged from a single ancestral species perhaps 10000 years ago.
Gradualism - modern theory of evolution
organisms descend from a common ancestro gradually over a long period of time in a linear or branching fashion.
Punctuated Equilibrium
the favored theory of evolution today. observed taht the gradualism thery was not supported by fossil record. New species appear suddenly after long periods of stasis.
