Uniformitarianism: The processes that made land forms then still make landforms now
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Charles Lyell (1830)
* Principle of geology * Change in Earth is gradually accepted
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Jean-Batiste de Lamarck
Earliest uncompromising advocate of evolution
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Lamarck’s Mechanism
1) INTERNAL forces—unknown internal mechanism causes differences between parent and offspring
2)Inheritance of ACQUIRED traits: use or disuse of trait alters trait through lifetime, which is then passed to offspring
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Darwin’s Two points
* descent with modification * Mechanism for the evolutionary process (natural selection)
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Two schools of thought
1) Mendelians
2) Biometricians
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Mendelians
Discontinuous Variation De Vries and Bateson
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Biometricians
Continuous Variation Weldon and Pearson
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Neo- Darwinism
EVOLUTION = HERITABLE VARIATION X SELECTION
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3 requirements for evolution by natural selection
1. (More offspring are produced \n than survive) 2. Variation among individuals 3. Inheritance of variation 4. Individuals with favorable characteristics are more likely to survive and reproduce \n **Differential survival and reproduction related to this variation–Selection**
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DNA
a molecule composed of two strands of nucleotides that are wound together into a double helix.
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Chromosome
compact structures consisting of long strands of DNA wound around proteins.
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Alleles
different forms of a particular gene.
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Polygenic
when a single trait is affected by several genes; enables phenotypes to span a range of values in a population (e.g., human body height). (often bell shaped)
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Pleiotropy
when a single gene affects multiple traits
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heterozygous
when an individual has two different alleles of a particular gene.
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Homozygous
when an individual has two identical alleles of a particular gene
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Codominant
When two alleles both contribute to the phenotype (e.g., flower color in snapdragons).
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Dominant
an allele that masks the expression of the other allele.
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Recessive
an allele whose expression is masked by another allele; most harmful alleles are recessive.
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Gene pool
collection of alleles from all individuals in a population.
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Random Assortment
the process of making haploid gametes in which the combination of alleles that are placed into a given gamete could be any combination of those possessed by the diploid parent.
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Mutation
a random change in the sequence of nucleotides in regions of DNA that controls the expression of a gene.
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Sources of genetic variation
* random assortment * mutation * recombination
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Recombination
the reshuffling of genes that can occur as DNA is copied during meiosis and chromosomes exchange genetic material.
a process that occurs when genetic variation is lost due to random variation in mating, mortality, fecundity, and inheritance.
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Bottleneck effect
a reduction of genetic diversity in a population due to a large reduction in population size (e.g., from loss of food). Survivors carry a fraction of the genetic diversity from the original population
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Founder effects
when a small number of individuals leave a large population to colonize a new area and bring with them only a small amount of genetic variation.
Genetic drift can cause additional reductions in genetic variation.
Genetic variation remains low until enough time has passed to accumulate new mutations.
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Natural selection
the process by which certain phenotypes are favored to survive and reproduce over other phenotypes.
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Stabilizing selection
when individuals with intermediate phenotypes have higher survival and reproductive success than those with extreme phenotypes.
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3 requirements for evolution by natural selection
1. Variation among individuals 2. Inheritance of variation 3. (More offspring are produced \n than survive) 4. Individuals with favorable characteristics are more likely to survive and reproduce \n
**Differences in survival and reproduction related to this variation–Selection**
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Hardy Weinberg principle
* A model used to quantify evolution * Null hypothesis—assumes no evolution * Gene pool—all the copies of all alleles in a population
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Hardy Weinberg requirements
* No migration * No mutation * No selection * Random mating * Large population size
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Hardy Weinberg equations
* 1=p2+2pq+q2 * 1=p+q
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Selection
some individuals survive/reproduce better
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Fitness
genetic contribution to next generation
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Relative fitness
fitness compared to other individuals
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Directional selection
Favors one extreme over another
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Stabilizing selection
Favors mean value (individuals who have the “extreme” traits do not survive and reproduce, but the organisms with the intermediate traits do)
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Disruptive selection
Favors both extremes (the intermediate traits do not survive and reproduce well)
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Microevolution
the evolution of populations; affected by random processes and selection.
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Artificial Selection
Selection in which humans decide which individuals will breed; breeding is done with a preconceived goal for the traits in the population (e.g., dogs, wild mustard).
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Industrial Melanism
a phenomenon in which industrial activities cause habitats to become darker due to pollution; individuals possessing darker phenotypes are favored by selection.
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Macroevolution
evolution at higher levels of organization including species, genera, families, orders, and phyla.
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Speciation
the evolution of a new species
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phylogenetic trees
hypothesized patterns of relatedness among different groups such as populations, species, or genera; depict which groups evolved from other groups.
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Allopatric speciation
the evolution of new species through the process of geographic isolation.
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Sympatric speciation
the evolution of new species without geographic isolation.
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polyploid
a species that contains three or more sets of chromosomes; can also give rise to sympatric speciation.
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Life history
the schedule of an organism’s growth, development, reproduction, and survival; represents an allocation of limited time and resources to achieve maximum reproductive success.
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Fecundity
the number of offspring produced by an organism per reproductive episode.
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Parity
The number of reproductive episodes an organism can experience
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Parental Investiment
the time and energy given to an offspring by its parents.
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Longevity (life expectancy)
the life span of an organism
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Slow life history (k-selected)
Long time to sexual maturity
Long life spans
Low numbers of offspring
High parental investment
Examples: elephants, oak trees
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Fast life history (r selected)
Short time to sexual maturity
Short life spans
High numbers of offspring
Little parental investment
Examples: fruit flies, weeds
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principle of allocation
the observation that when resources are devoted to one body structure, physiological function, or behavior, they cannot be allotted to another.
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trade off between number and size
The more offspring an organism produces the smaller those organisms are going to be
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Determinate growth
a growth pattern in which an individual does not grow any more once it initiates reproduction; occurs in many species of birds and mammals.
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Indeterminate growth
a growth pattern in which an individual continues to grow after it initiates reproduction; occurs in many species of plants, invertebrates, fishes, reptiles, and amphibians.
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Semelparity
when organisms reproduce only once during their life; relatively rare in vertebrates, but common in insects and plants.
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Iteroparity
when organisms reproduce multiple times during their life; common among birds, reptiles, mammals, and amphibians.
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Annual
organism with a lifespan of one year
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Perennial
An organism with a lifespan of more than one year
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Senescence
a gradual decrease in fecundity and an increase in the probability of mortality.
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What induces change
* Proximate—indirect cues, do not affect fitness directly * Ultimate—directly affect fitness
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photoperiod
the amount of light that occurs each day; provides a cue for many events in the life histories of virtually all organisms.
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Viscosity
he thickness of a fluid that causes objects to encounter resistance as they move through it.
Water’s viscosity is high
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Adaptations to water viscosity
* Streamlined bodies reduce drag * Tiny marine animals rely on drag for movement, evolved long, filamentous appendages
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Adaptations to water density
Many fish have gas-filled swim bladders that can equalize their density with that of the surrounding water.
Some algae use droplets of oil as floatation devices.
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Solutes
dissolved substances in water
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Semipermeable Membrane
membranes that allow only particular molecules to pass through; reduces free movement of solutes.
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Osmoregulation
mechanisms organisms use to maintan a proper solute balance.
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Hyperosmotic
tissue solute concentrations are higher than surrounding water.
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Hypoosmotic
tissue solute concentrations are lower than surrounding water.
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Countercurrent circulation
is an adaptation where blood and water flow in opposite directions so that the concentration of O2 in water is always greater than the concentration in blood.
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Anaerobic or anoxic
environment becomes completely devoid of oxygen
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Thermophilic
heat loving
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**Glycerol** and **glycoproteins**
chemicals present in some animals (e.g., Arctic cod) that prevent freezing by reducing strength of hydrogen bonds or via **supercooling** (i.e., coating of ice seeds).
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Thermal Optima
the range of temperatures in which an organism best performs.
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Isozymes
different forms of an enzyme that catalyze a reaction.
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Cohesion
the mutual attraction of water molecules; allows water to move up through empty remains of xylem cells.
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root pressure
when osmotic potential in the roots of a plant draws in water from the soil and forces it into xylem; can raise water to \~20 m.
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Transpiration
the process by which leaves can generate water potential as water evaporates from the surfaces of leaf cells.
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Stomata
small openings on leaf surfaces that are points of entry for CO2 and exit points for water vapor; bordered by *guard cells* that open and close each stoma.(stop excess transpiration so plants do not wilt)
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Electromagnetic radiation
energy from the Sun; packaged in small, particle-like units called *photons*.
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Photosynthetically active region
**:** wavelengths of light that are suitable for photosynthesis; includes wavelengths from 400 nm (violet) to 700 nm (red).
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chloroplasts
specialized cell organelles found in eukaryotic photosynthetic organisms.
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Photosynthesis
the process of combining CO2, H2O, and solar energy to produce glucose (C6H12O6):
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C3 photosynthesis
uses 3 carbon compounds and uses rubisco as a catalyst
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Disadvantages of C3 photosynthesis
Rubisco is inefficient \n Low affinity for CO2, so plants need large amounts
Rubisco also preferentially binds to O2.
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C4 photosynthesis
a photosynthetic pathway in which CO2 is initially assimilated into a four-carbon compound, oxaloacetic acid (OAA); provides an advantage in hot and dry conditions.