General Ecology Exam 2

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phenotype

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The manifestation of a trait in an individual

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genotype

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The genetic constitution of an individual that along with the environment determines the phenotype

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gene pool

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the sum total of all the alleles in a population

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genetic drift

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stochastic (RANDOM) shift in allele frequency Drift can occur in both large and small population but the effect is exaggerated in smaller population. As drift is occurring differences in allele frequency will keep occurring and loss or fixation will result in bimodal distribution.

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Ne – effective population size

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The major determining factor is effective population size which is defined as the number of individual participating in random mating. Any factor that can limit interbreeding will lower this number such as sex proportion (1:1), population size fluctuations, variation in number of offspring. Natural selection can lower Ne also if generations overlap If Ne declines too much extinction can occur.

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gene flow

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the net movement of alleles into or out a population

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natural selection

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The differential representation of genotypes in future generations is resulting from heritable differences among them in survival and reproduction.
1. Inheritable variation exist amongst individuals in a population
2. Resources or limited
3. Those who are better suited to maximize and gather limited resources will be more likely to grow and leave more offspring

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fixed

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Both genetic drift and natural selection can result in an allele being the only allele at that genetic locus in the population. Geneticists refer to this outcome by saying that the allele has been fixed in the population. Of course, if one allele is fixed, that implies that all other alleles have been lost from the population. Thus, genetic drift and natural selection can both lead to the loss of alleles—and hence, genetic variability—in populations.

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fitness

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is the relative genetic contribution by an individuals descendents to future generation absolute fitness is the expected number of offspring produced by a particular phenotype this take into account survival ability relative fitness just takes account the genotype representation in a population
1. Fitness is a property of genotype, individuals with the same genotype have the same fitness
2. It is specific to a particular environment
3. Fitness is measured over one generation or more

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convergent evolution

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similar adaptations in organisms with different phylogenetic histories

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evolution

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genetic change in a population over time the process of long term development and change in living organisms as a result of processes such as natural selection, genetic drift, and speciation

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adaptation

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an evolutionary solution to an ecological problem , features of an organism that increases fitness

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non adaptive evolution

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Another theory of evolution is called "genetic drift", "neutralism" or "nonadaptive evolution". In the Darwinian view, all of an organism's traits are the result of natural selection, which continuously weeds out unsuitable variations and selects suitable ones to be retained in the next generation. However, in at least some instances, the presence of a particular genetic trait may be solely the result of chance. In a small population in which a portion of the members possessed one trait and a portion possessed another, it is possible for an accidental set of circumstances such as a disease or natural disaster to wipe out all of those possessing one of these traits, leaving only one trait left. Thus, this trait would be retained not through natural selection, but solely because of fortuitous circumstances. This is often referred to as "survival of the luckiest".

There also seem to be a large number of traits which are equal in their "fitness"; none has any selection advantage over the others. In this manner, these traits are said to be "neutral"--they are neither selected for nor selected against, and the proportion of one trait to another in a population can change haphazardly through purely statistical methods.

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sampling error

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Random error occurs when we take a sample of a variable population, and by chance the sample does not perfectly represent the real population. This is always present to some degree, because populations are naturally variable. Random errors:

unpredictably make estimates either too large or too small
have larger effects if our sample size is small, so to decrease the impact of random error, increase sample size.

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coalescence

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- the merging of genetic lineages backwards time to a most recent common ancestor

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deme

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small individual populations) that are initially genetically identical evolve by chance to have different genetically identical constitutions

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meta population

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a population of populations a group of discrete populations connected by potential and actual routes of dispersal

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founder effect

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restrictions in size through which populations may pass are called bottlenecks when a new population is established by a small number of colonists

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bottleneck

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a pattern of population change in which the population is reduced to small numbers and then expands again

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species diversity

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the number of species and the heterogeneity of their abundances in a community

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species richness

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the total number of species in a community

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evenness

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the degree to which the number of individuals in evenly distributed among species in a community

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habitat islands

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some habitats are islands because they are surrounded by inhospitable country that serves as a barrier to dispersal

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volatile cycle

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includes gaseous materials such as oxygen and carbon dioxide

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sedimentary cycle

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non volatile materials like phosphorous the most important cycles of the four elements most crucial to life is the carbon, nitrogen, phosphorous, and sulfur cycle

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adiabatic cooling

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a decrease in air temperature at higher elevations as a result of decreasing air pressure

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maritime climate

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climate of a region near a large body of water characterized by small annual temperature fluctuations

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continental climate

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a climate of large land masses, as distant from large bodies of water, characterized by large annual temperature fluctuations

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biome

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a major unit of terrestrial vegetation characterized by the structure of the plant community

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Hardy weinberg equation

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(p² + 2pq + q² = 1
Violations of the Hardy–Weinberg assumptions can cause deviations from expectation. How this affects the population depends on the assumptions that are violated. Generally, deviation from the Hardy-Weinberg equilibrium denotes the evolution of a species.

Random mating. The HWP states the population will have the given genotypic frequencies (called Hardy-Weinberg proportions) after a single generation of random mating within the population. When violations of this provision occur, the population will not have Hardy-Weinberg proportions. Three such violations are:
Inbreeding, which causes an increase in homozygosity for all genes.
Assortative mating, which causes an increase in homozygosity only for those genes involved in the trait that is assortatively mated (and genes in linkage disequilibrium with them).
Small population size, which causes a random change in genotypic frequencies, particularly if the population is very small. This is due to a sampling effect, and is called genetic drift.

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What are the conditions and violations of Hardy-Weinberg equilibrium

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1. mutation is not occurring
2. natural selection is not occurring
3. the population is infinitely large
4. all members of the population breed
5. all mating is totally random
6. everyone produces the same number of offspring
7. there is no migration in or out of the population

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What are Darwin’s three points about natural selection?

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The differential representation of genotypes in future generations is resulting from heritable differences among them in survival and reproduction.
1. Inheritable variation exist amongst individuals in a population
2. Resources or limited
3. Those who are better suited to maximize and gather limited resources will be more likely to grow and leave more offspring

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Describe the three modes of natural selection

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directional, disruptive, stabalizing selection

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Directional Selection

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occurs when selection favors one extreme trait value over the other extreme. This typically results in a change in the mean value of the trait under selection.

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Disruptive Selection

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occurs when selection favors the extreme trait values over the intermediate trait values. In this case the variance increases as the population is divided into two distinct groups. Disruptive selection plays an important role in speciation.

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Stabilizing Selection

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occurs when selection favors the intermediate trait value over the extreme values. Populations under this type of selection typically experience a decrease in the amount of additive genetic variation for the trait under selection.

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What are three major causes of random genetic drift? Describe in detail

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In very small populations, genetic drift can be strong enough to override selection, and it may cause fixation of even initially frequent alleles. Because of the random loss of alleles, genetic drift may cause loss of genetic diversity
Inbreeding: is the mating between related individuals and may also cause loss of diversity. If inbreeding results in the expression of recessive deleterious alleles in homozygous offspring, their fitness may be reduced (inbreeding depression). In contrast to genetic drift, inbreeding causes a reduction in genetic diversity, but not a change in allele frequencies.
Migration (gene flow) is the main homogenizing force. Individuals, which move from one subpopulation to another and reproduce will introduce alleles from a different subpopulation (and thus genetic diversity), and will therefore homogenize the two populations genetically. The effect of migration depends on the number of migrants, rather than migration rate, and only very few migrants can homogenize populations completely.

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Describe five causes for lower Ne.

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Unequal number of breeding males and females (sex ratio)
Unequal reproductive success
Changes in population size through time (cataclysmic events)
Bottlenecks
Founder Effects

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What is the Shannon-Weaver index? How does it measure species diversity?

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is one of several diversity indices used to measure diversity in categorical data. It is simply the Information entropy of the distribution, treating species as symbols and their relative population sizes as the probability.

This article treats its use in the measurement of biodiversity. The advantage of this index is that it takes into account the number of species and the evenness of the species. The index is increased either by having additional unique species, or by having a greater species evenness.

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What is the total species richness of the planet? Why is this number controversial?

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must adapt indirect methods evolution happens most in the tropics and .5 percent of the worlds mass may contain 20 percent of the worlds species

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non-equator latitudes

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species richness decreases with increasing latitude high species diversity in the tropics

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ecotones

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the boundary between two habitats greater diversity in an ecotone than the supporting habitat

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deep ocean

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difficulty in sampling fllors led to a misconception that there will be no biodiversity there the number of species are increasing as better sampling techniques are be established

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island biodiversity

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have fewer species than on main land extinction rates are a function of island size not distance immigration rates are a function of distance

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major determinants of climate

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temp, water availability, altitude, latitude, slope effect

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tundra

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derived from the word that means treeless plain flora is varied climate is quite severe Tundra is the coldest of all the biomes. Tundra comes from the Finnish word tunturi, meaning treeless plain. It is noted for its frost-molded landscapes, extremely low temperatures, little precipitation, poor nutrients, and short growing seasons. Dead organic material functions as a nutrient pool. The two major nutrients are nitrogen and phosphorus. Nitrogen is created by biological fixation, and phosphorus is created by precipitation

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coniferous forests

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The coniferous forests are located in the northern hemisphere and stretch across the North American, Europe, and Asia continents. These coniferous forests are also known as the "taiga" or "boreal" forest. The trees that make up the forest are cone-bearing trees like the pine, fir, spruce and hemlock. These evergreen trees have needle-like leaves that keep their green color all year long. These trees have a shallow root system. The coniferous forests have short warm summers and long, cold winters lasting up to seven months.

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desert

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evaportation exceeds precipitation

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deciduous forest

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composed of trees that drop their leaves seasonally high diversity of trees

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Why are tropical forests so important to the planet?

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the most extensive forest systems on the planet that grow near equator rainfall is high species diversity is the greatest here

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carbon cycle

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virtually almost all plants use CO2 as the source of carbon to make carbs and can accumulate in the form of fossil fuels

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nitrogen cycle

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nitrogen fixation from nitrogen fixers who convert molecular nitrogen to a more useful form

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SLOPE EFFECT

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for any giving mountain on either side of a range west and south facing slopes will be hotter and drier than the east and north facing slope

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essentialism

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plato philosophy variation is accidental imperfection

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Darwins evolutionary theory

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decent with modification it holds that all species living and extinct have decended without interuption from one or a few original forms of life

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microevolution

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is the occurrence of small-scale changes in allele frequencies in a population, over a few generations

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macroevolution

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is evolution on a grand scale—what we see when we look at the over-arching history of life: stability, change, lineages arising, and extinction

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Classification

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Classification is a very broad term which simply means putting things in classes. Any kind of organisational scheme is a classification: for example, sorting smarties by colour, coins by diameter or cities by population. Humans seem unable to resist the urge to classify. It's one of the most basic activities of any science, because it's easier to think about a few groups of things than about lots of separate things.

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Taxonomy

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means giving names to things. It tends to go hand in hand with classification, but need not. You can arrange things without naming them, or name them without arranging them, but the most helpful schemes name things in a way the reflects their classification

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Phylogeny

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Phylogeny is the ``tree of life'' - the hierarchical structure by which every life-form is related to every other life-form. The word phylogeny refers to the reality of that tree - the one, true, tree - as opposed to the theories that people make about it. So phylogeny is not an activity (something that we do), but a fact (something that we try to discover.)

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Systematics

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is the process of trying to classify animals (or plants) according to their phylogeny. We could describe the systematics of a group at any moment as being the best current approximation to its phylogeny - because the phylogeny is a solid, unchanging thing, but our systematics will change as we discover more information. (For example, the Therizinosauria were widely considered to be related to the prosauropods until the discovery of the basal therizinosaur Beipiaosaurus showed that they were coelurosaurs.)

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Cladogenesis

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is the branching or multiplication of lineages, each of which evolves along its own path. also known as phylogenetic systematics, is a relatively new way of doing systematics. It works by analysing different taxa to find objective similarities and differences between them, and using those similarities and differences to derive a hierarchical structure showing which taxa are most similar to others

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biological species concept

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species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups

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Evolutionary species concept

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a species is a single lineage and ancestor decendant sequence of populations or organisms that maintains an identity seperate from other such lineages and which has its own evolutionaty tendencies and historical fate

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Phylogenetic species concept

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1. a phylogenetic species is an irreducible basal cluster of organisms that is diagnosably distinct from other such clusters, and within whichthere is a parental pattern of ancestry and decent 2. a species is the smallest monophyletic group of commmon ancestry

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Genealogical species concept

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species are exclusive group of organisms where an exclusive group is one whose members are all more closely related to one another than to any organism outside the group

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Recognition species concept

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a species is the most inclusive population of individual biparental organisms that share a common fertilization system

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Cohesion species concept

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a species is the most inclusive population of individuals having the potential for the phenotypic cohesion through intrinsic cohesion mechanisms

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geographic isolation

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reduction or prevention of gene flow between populations by an extrinsic barrier movement such as topographic features or unfavorable habit

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allopatric populations

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populations occupying seperated geographic areas

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sibling species

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reproductively isolated species that are difficult to distinguish by morphological characteristics

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Allopatric speciation

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is the evolution of reproductive barriers in populations that are prevented by a geographic barrier from exchanging genes at more than a negligible rate

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vicariance

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divergence of two large population (allopatric speciation)

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peripatric speciation

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divergence of small populations from a widely distributed ancestral form

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parapatric speciation

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neighboring populations between which there is modest gene flow diverge and become reproductively isolated

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Sympatric speciation

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is the evolution of reproductive barriers within a single initially randomly mating population

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Dollo's law

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in general its seems likely that complex characters once lost are not regained

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punctuated equilibria

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refers to both the pattern of change in the fossil record and a hypothesis about evolutionary processes. a common pattern is long periods in which species exhibit little on no phenotypic changes and the statsis is punctuated by rapid change in contrast there is phyletic gradualism the traditional notion of slow incremental change