Biology Chapter 19 Notes by img20336


									Biology Chapter 19 Notes
   - Descent with modification is long-term change in inherited characteristics
   - Different species arose as a result of inherited variation in populations, giving
       some an improved chance to survive/reproduce.
   - Evidence of evolution includes fossils, the record of ancient organisms. The fossil
       record in different strata of the earth shows the order of evolutionary change.
       Palentology is the study of fossils.
   - Examples of the appearance of new species from ancestral ones include diatoms,
       singled-celled photosynthetic organisms that live in water, have hard shells that
       can be preserved as fossils.
   - Harder parts of animals, like bone, survive decay. Harder minerals replace the
       original substance of animal parts and preserve them as fossils. Softer tissue
       leaves an impression on soft mud that dries. Ancient insects were preserved when
       trapped in tree sap that became amber.
   - The fossil record, though it contains about 300,000 species of fossils, is
       incomplete because most dead organisms decay and do not become fossils.
   - Fossils offer physical record of organisms not found on earth today; you can
       compare fossils in younger, shallower rock with that of older, deeper rocks.
   - Extinction occurs much more often because of increasing human population,
       which in turn changes the environment, such as the passenger pigeon. Also,
       overhunting can be an issue.
   - Fossils record organisms before/after new species split off from older ones. They
       show the rate of evolutionary change and show intermediate stages between
       species and their ancestors. They have uncovered “feathered dinosaurs”,
       suggesting the birds evolved from dinosaurs.
   - While Darwin was aboard the beagle, he examined many things, including the
       Galapagos tortoises. On islands where cacti, its food, grew high on tough woody
       stems, the tortoises’ necks were long and their shells were saddleback. On islands
       where the cacti is low-growing, the tortoises are normal necked and shelled. This
       shows coevolution, the continuous adaptation of different species to each other.
   - This is also found in the adaptations of predator and their prey: for example, we
       have bitter tastes and don’t like it: this protects us from plant toxins. Symbiotic
       species have coevolved to the point where neither can survive without the other.
   - Artificial selection is one way to drive evolution experimentally: breeders choose
       who can mate, however. Natural selection states that members of a population
       members with the most adaptations to their environment are most likely to survive
       and reproduce.
   - Moth-eating birds was responsible for changes in the colors of peppered moths.
   - Dice conducted an experiment with buff-colored or grey mice and barn owls.
       Dice alternated the color of soil on the floor of a room each day with sticks. 4
       mice of each color were released and exposed to an owl for 15 minutes. One set
       of mice, depending on the soil color, survived up to twice as much as the other set
       of mice.
   - Homologies are similarities in the structure of an organism, like anatomy,
       behavior, and its polymers.
-   Homologous genes are responsible for the formation of the body plan and organs
    even in very distantly related species.
-   Since inheritance was poorly understood, he couldn’t defend his theory of
    evolution by natural selection.
-   Variation is found in mutations and the recombination of alleles in sexually
    reproducing eukaryotes (crossing over, independent assortment, and fertilization).
-   Genetic variation is the raw material of evolution.
-   Gene duplication produces gene families (multiple copies of nearly identical DNA
    sequences). Some of the copies, pseudogenes, are not expressed; they are not
    subjected to natural selection. This means that pseudogenes accumulate mutations
    faster than functional genes in the same family.
-   Scientists compare amino-acid sequences and nucleotide sequences of
    homologous proteins and genes. An example is the a and B form of globin. They
    are very closely similar. Anatomy and these genes support the hypothesis that all
    vertebrates share a common ancestor. This is also shown in Hox genes.
-   Many strains of bacteria that were killed by antibiotics have evolved to be
    resistant, such as tuberculosis. The more they’re exposed, the more the new
    population will be resistant. This has also led to pesticide-resistant insects.
-   Mutation is common in short repeated nucleotide sequences (microsatellites).
    They increase genetic variation. This occurs in the bacteria Neisseria gonorrhoeae
    and determine whether the bacteria can infect a person and case gonorrhea. Some
    cause the disease and others survive without causing it.
-   The microsatellites ensure that at least some bacteria can survive.
-   Speciation is the appearance of a new species. They include hybrids, such as the
    breeding of a Labrador and a German shepherd to create a mutt. Artificial
    selection includes them, such as creating new fruit flies by exposing some species
    to radiation.
-   Populations evolve, not individual organisms within a population. Genetic
    changes indicate that evolution is taking place. A gene pool that is in a state of
    equilibrium has a frequency of alleles that tends to remain stable.
-   Special in sexually reproducing organisms occurs when two populations become
    so different in their genetic makeup that they can no longer interbreed. Sometimes
    new species out-compete and replace the species that they originated from.
    Mostly, a small population is isolated from the rest of species and develops into a
    new species.
        o Geographic isolation (water, mountain range, impassable canyon) (Ex:
             tufted-ear squirrels)
        o Ecological isolation: two populations adapt to different habitats (willow
             flycatcher – brushy slopes; alder flycatcher – alder swamps)
        o Mating behavior and physical characteristics are important in the
             reproductive success of some organisms: sometimes gametes are not
             chemically compatible. Also, differences in size of the organisms or
             size/shape of their reproductive organs.
        o Behavioral isolation – mating pattern of a small group of organisms
             becomes different from that of the main group (reproductively isolated)
             (Ex: leopard frog – differences in premating behavior)
         o Seasonal isolation - The leopard frog populations mate at slightly different
             times during the year. This occurs in plants and animals – flowering at
             different times (pollen cannot pollinate carpels)
         o Isolation mechanisms – those that occur prior to and after zygote
             formation (Prezygotic – geographic isolation, mismatched mating
             behavior, seasonal isolation. Gametes never meet/fuse. Postzygotic –
             failure of the zygote to develop normally due to differences in parents).
         o Matings between individuals of related species often produce offspring
             that cannot produce normal gametes, making for an infertile thing.
         o Polyploidy is duplication of chromosomes that often makes a new species
             of plant. Offspring cannot mate successfully since other plants have the
             parental genes. This forces them to reproduce asexually or forces them to
             mate with other polyploidy offspring, establishing a new species.
         o Cross-species hybrid plants reproduce asexually. In time, a chromosome
             duplication in a hybrid plant can produce a tetraploid new species.
         o When a population enters an environment with few competing species, it
             often divides into several smaller populations, which avoid competing
             with each other by adapting or by using different resources in the same
             habitat. Then each population can become a new species. (Adaptive
         o Stasis is the large-scale change that remains very slow for a long period of
             time. Sometimes “living fossils,” which have changed very little from
             their ancestors, appear, like lungfish and the horseshoe crab. These live in
             an isolated, stable environment with little competition.
         o Gradualism is when evolutionary change/speciation occurred through
             gradual and fairly constant changes.
         o Punctuated equilibrium involves a short period of rapid change just after a
             population becomes isolated and forms a new species, and then slows
             down and approaches stasis.
         o These two patterns are extremes in evolution.
         o Selective pressure acts on the raw material of genetic variation to produce
             heritable, long-term change in living populations.
-   Hurton (chemical/physical processes as one rock changes into another), Smith
    (cut canals and observed strata with embedded fossils), and Lyell saw geologoical
    time. More evidence is found in radioactive decay. The Rb-87 isotope decays very
    slowly into Sr-87. The ratio of these isotopes in a rock/fossil is used to calculate
    its age. (and with others as well)
-   An “icebox fossil” was recovered whole from Siberia in 1999. It was a soft-tissue
    woolly mammoth. It was preserved very well. It is called the Jarkov mammoth.
-   Japanese hope to revive the mammoth. They will try to crossbreed a mammoth
    with an elephant by trying to remove the sperm intact. The mammoth, however
    has 58 chromosomes while the elephant has 56, even though they share a close
    genetic homology. DNA are about 5% different.
-   They could also try to use DNA or a cell nucleus to try to clone the mammoth.
-   The fossil record provides evidence of the rate of evolutionary change. They
    indicate that anatomical structures do not change at a constant rate. It’s more
    constant for a particular DNA or protein sequence. But the rate for a functional
    part of a protein is slower than a change in the less functional parts of the
    molecule (like the surface parts).
-   A unit of evolutionary change is called a darwin, which is the change in a
    characteristic being studied by a factor of e (2.718) in 1 million years. They can
    measure it since it’s possible to count the number of changed bases in DNA or
    amino acids in a protein
-   A species can become extinct if its habitat has been destroyed or its environment
    changed. Evolutionary changes can also affect other species in the same
    environment. Sometimes, environments have changed so quickly that a lot of
    species died out.
-   The last mass extinction occurred about 65 million years ago: the climate cooled,
    and a lot of things died out. At least two asteroids or comets struck Earth while
    these extinctions occurred. (Iridium). Alvarez studied it and concluded it was
    from dust. However, the extinctions, though large, were not abrupt.
-   Advantages to mass extinctions: vacated habitats, ensures survival/dispersal for
    the survivors

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