Ecology Exam 2

James Hutton (1788)

Uniformitarianism: The processes that made land forms then still make landforms now

Charles Lyell (1830)

• Principle of geology

• Change in Earth is gradually accepted

Jean-Batiste de Lamarck

Earliest uncompromising advocate of evolution

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​

Darwin’s Two points

• descent with modification

• Mechanism for the evolutionary process (natural selection)

Two schools of thought

1. Mendelians

2. Biometricians

Mendelians

Discontinuous Variation​ De Vries and Bateson​

Biometricians

Continuous Variation​ Weldon and Pearson​

Neo- Darwinism

EVOLUTION = ​ HERITABLE VARIATION X SELECTION​

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​

DNA

a molecule composed of two strands of nucleotides that are wound together into a double helix.​

Chromosome

compact structures consisting of long strands of DNA wound around proteins.​

Alleles

different forms of a particular gene.​

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

heterozygous

when an individual has ​two different alleles of a particular gene.​

Homozygous

when an individual has ​two identical alleles of a particular gene

Codominant

When two alleles both ​contribute to the phenotype (e.g., flower color in snapdragons).​

Dominant

an allele that masks the expression of the other allele.​

Recessive

an allele whose expression is masked by another allele; most harmful alleles are recessive.​

Gene pool

collection of alleles from all individuals in a population.​

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.​

Mutation

a random change in the sequence of nucleotides in regions of DNA that controls the expression of a gene.​

Sources of genetic variation

• random assortment

• mutation

• recombination

Recombination

the reshuffling of genes that can occur as DNA is copied during meiosis and chromosomes exchange genetic material.​

Mechanisms of Evolution

• mutation

• migration

• genetic drift

• selection (natural selection)

• Selection(sexual selection or non-random mating)

Genetic drift

a process that occurs when genetic variation is lost due to random variation in mating, mortality, fecundity, and inheritance.​

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

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.​

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Genetic drift can cause additional reductions in genetic variation.​

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Genetic variation remains low until enough time has passed to accumulate new mutations.​

Natural selection

the process by which certain phenotypes are favored to survive and reproduce over other phenotypes.​

Stabilizing selection

when individuals with intermediate phenotypes have higher survival and reproductive success than those with extreme phenotypes.​    

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​

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​

Hardy Weinberg requirements

• No migration​

• No mutation​

• No selection​

• Random mating​

• Large population size​

Hardy Weinberg equations

• 1=p2+2pq+q2​

• 1=p+q​

Selection

some individuals survive/reproduce better​

Fitness

genetic contribution to next generation​

Relative fitness

fitness compared to other individuals​

Directional selection

Favors one extreme over another

Stabilizing selection

Favors mean value (individuals who have the “extreme” traits do not survive and reproduce, but the organisms with the intermediate traits do)

Disruptive selection

Favors both extremes (the intermediate traits do not survive and reproduce well)

Microevolution

the evolution of populations; affected by random processes and selection.​

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).​

Industrial Melanism

a phenomenon in which industrial activities cause habitats to become darker due to pollution; individuals possessing darker phenotypes​ are favored by selection.​

Macroevolution

evolution at higher levels of organization including species, genera, families, orders, and phyla.​

Speciation

the evolution of a new species

phylogenetic trees

hypothesized patterns of relatedness among different groups such as populations, species, or genera; depict which groups evolved from other groups.​

Allopatric speciation

the evolution of new species through the process of geographic isolation.​

Sympatric speciation

the evolution of new species without geographic isolation.​

polyploid

a species that contains three or more sets of chromosomes; can also give rise to sympatric speciation.​

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.​

Fecundity

the number of offspring produced by an organism per reproductive episode.​

Parity

The number of reproductive episodes an organism can experience

Parental Investiment

the time and energy given to an offspring by its parents.​

Longevity (life expectancy)

the life span of an organism

Slow life history (k-selected)

Long time to sexual maturity​

Long life spans​

Low numbers of offspring​

High parental investment​

Examples: elephants, oak trees​

Fast life history (r selected)

Short time to sexual maturity​

Short life spans​

High numbers of offspring​

Little parental investment​

Examples: fruit flies, weeds​

principle of allocation

the observation that when resources are devoted to one body structure, physiological function, or behavior, they cannot be allotted to another.​

trade off between number and size

The more offspring an organism produces the smaller those organisms are going to be

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.​

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.​

Semelparity

when organisms reproduce only once during their life; relatively rare in vertebrates, but common in insects and plants.​

Iteroparity

when organisms reproduce multiple times during their life; common among birds, reptiles, mammals, and amphibians.​

Annual

organism with a lifespan of one year

Perennial

An organism with a lifespan of more than one year

Senescence

a gradual decrease in fecundity and an increase in the probability of mortality.​

What induces change

• Proximate—indirect cues, do not affect fitness directly​

• Ultimate—directly affect fitness​

photoperiod

the amount of light that occurs each day; provides a cue for many events in the life histories of virtually all organisms.​

Viscosity

he thickness of a fluid that causes objects to encounter resistance as they move through it.​

Water’s viscosity is high​

Adaptations to water viscosity

• Streamlined bodies reduce drag​

• Tiny marine animals rely on drag for movement, evolved long, filamentous appendages​

Adaptations to water density

Many fish have gas-filled swim bladders that can equalize their density with that of the surrounding water.​

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Some algae use droplets of oil as floatation devices.​

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Solutes

dissolved substances in water

Semipermeable Membrane

membranes that allow only particular molecules to pass through; reduces free movement of solutes.​

Osmoregulation

mechanisms organisms use to maintan a proper solute balance.​

Hyperosmotic

tissue solute concentrations are higher than surrounding water.​

Hypoosmotic

tissue solute concentrations are lower than surrounding water.​

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.​

Anaerobic or anoxic

environment becomes completely devoid of oxygen

Thermophilic

heat loving

**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).

Thermal Optima

the range of temperatures in which an organism best performs.​

Isozymes

different forms of an enzyme that catalyze a reaction.​

Cohesion

the mutual attraction of water molecules; allows water to move up through empty remains of xylem cells.​

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.​

Transpiration

the process by which leaves can generate water potential as water evaporates from the surfaces of leaf cells. ​

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)

Electromagnetic radiation

energy from the Sun; packaged in small, particle-like units called *photons*.​

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.​

Photosynthesis

the process of combining CO2, H2O, and solar energy to produce glucose (C6H12O6):​

C3 photosynthesis

uses 3 carbon compounds and uses rubisco as a catalyst

Disadvantages of C3 photosynthesis

Rubisco is inefficient​ \n Low affinity for CO2, so plants need large amounts​

Rubisco also preferentially binds to O2.​

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.​

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Attributes of C4 photosynthesis

4 carbon compound and uses PEP as a catalyst

CAM(**crassulacean acid metabolism) photosynthesis**

a pathway in which the initial assimilation of carbon into OAA occurs at night.​

Homeostasis

an organism’s ability to maintain constant internal conditions in the face of a varying external environment.​

Negatives feedbacks

The action of internal response mechanisms that restores a system to a desired state, or set point, when the system deviates from that state.​

Sources of heat gain and loss

• radiation

• conduction

• convection

• evaporation

Radiation

the emission of electromagnetic energy by a surface.​

Increases with the fourth power of absolute temperature​

Conduction

the transfer of the kinetic energy of heat between substances that are in contact with one another.​

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depends on surface area, resistance of substances to heat transfer, and temperature differences between substances