First Exam Flashcards
Evolutionary population
When a Group of the same organisms Gene pool changes and they go through evolutionary change.
Microevolution
Change in gene pool. Ex: frequency of alleles due to an individual phenotypic traits that are better to survive and reproduce. How biotic and abiotic selective agents change the gene pool with each generation.
Phenotypes
Observable, measurable characteristics of organisms. Hi eggy, eye color and blood type
Natural selection-
The major process that changes gene pools in nature. Expect to occur in all populations. It is a law of nature.
Artificial selection
Humans choose which animals or plants to breed because they want a desirable characteristics. Goal of developing particular phenotypic characteristics. Pg 41
Relative fitness
Genetic contribution (typically the number of surviving offspring) of an individual to succeeding generations. Compared to surviving offspring of other members of species.
Components of fitness
Growth, survival and reproduction.
Agents of selection
Any environmental factor that causes variation in survival and reproduction of individuals. Agent of natural selection. Can be abiotic (climate: rain fall, temp, light availability. Edaphic: soil minerals soil PH, soil moisture) and biotic (macroscopic- competitor inter and intraspecific) pg 8
G x E
When two or more genotypes react to an environmental factor in different ways. A norm or reaction graph is used to display the genotypes reactions. Fig 2.3 dandelion in mown vs unmown habitats
Directional selection
Mean changes over time. Phenotypes with larger or smaller values of the trait show greater relative fitness and are thus favored by selection. Pg 22
Changes in weather, climate or food availability lead to directional selection.
Contemporary evolution
Evolution which occurs in less then 100 years
Stabilizing selection
Favors the average individuals in a population. Mean does not change. Selects against extreme Phenotypes and favors those adapted to the environment.
Disruptive selection
Phenotypes with the intermediate trait values show the lowest relative fitness. Natural selection favors extreme variations of a trait. Pg 22 can lead to two distinct groups
External vs internal
Agents of selection
External factors- outside the organism ex: soil ph
Internal agents- selection pressures derive from the internal dynamics of a functioning organisms. bio chemicals, growth factors and living endosymbiotic microbes
Selection differential
Simple linear regression. Measure of the intensity of selection. Covariance of fitness with trait values.
Fitness function
Selection gradient
Statistical correlation of trait you are interested in vs. other traits you measured
Path analysis
Uses multiple regression on different phenotypic traits correlated with the trait of interest and also inter correlated (among themselves) . Promise for improving the understanding of selection by permitting a way to evaluate different hypothesizes causal pathways of selection.
Natural experiments pg 39
Usually studies a distinct recognizable phenotypic variant that already exist in one or more populations. No selective agents are manipulated, fitness of discrete Phenotypes is monitored under natural conditions. You see different phenotypic traits in population.
Common Garden
Grow organisms in homogenous common environment to reveal possible genetic/phenotypic differences and indicates much potential for natural selection to cause evolutionary change. In populations, families, clones, ecotypes.
“In vitro” ecology
Study of ecotypic differentiation.
Can be useful in identifying and evaluating specific genotypes, populations and ecotypes of a particular plant species in terms of their life history features. Pg 46 corms on trees.
Single garden experiment
Has been used a long time in plant ecology history. Can show certain results if environmental factors are varied experimentally. Do not allow the detection of pop by env interactions. Can show different variations in pop from a common env.
Ecotype
A genetically distinct population of plants, animals or organisms that are found in a particularly habitat adapted to specific to environment.
Turesson
1920s in Sweden, he came up with the Ecotype concept (locally adapted population that show distinct phenotypic traits)
Geographic cline
When a species or Ecotype has specific phenotype or genetic trait due to geographic area.
Multiple gardens
No env. Factors varied. Can measure population (or genotype) by environmental interaction.
Eg) Clausen, Keck and Heisy Sierra Nevada three common gardens different elevations. Learn GxE interactions, important to understand evolution of local adaption.
Home- site advantage
Garden population did best when conditions matched original/ home environment. Mostly climate situations
Multiple common gardens one or more env factors varied
Usually env. Factors thought to be important selection agents are varied by experiments. Expected pop. To perform beat when exposed to conditions similar to their original “home” environment.
Agents responsible for adaptive differentiation of populations.
Blocking. Block-type experimental designs
To control for possible unidentified variation in environmental conditions within a common garden. Treating statically heterogeneity as an effect in an analysis of variance. One part of the garden can have different factors than another. Such as sun hours or soil minerals.
Questions and considerations in using common garden experiments
- what to use: seeds, seedling or ramets?
- control for “maternal effects?
- How many gardens? Where will they be places?
- What sample sizes to use?
- Will “blocks” be used to control heterogeneity?
- Will naturally occurring vegetation be removed or not?
- Will climate/env data be obtained from poo source regions?
- Will any env variables by purposely manipulated?
Usefulness and applications of common garden technique pg 65
- investigation of invasive plants, can reveal which phenotypic traits are under selection and likely to be important to invasion success.
- adaption to climate change- expect plant from southern pop to be well suited for increasing temps
- study hybrid fitness
- testing effects of genetically engineered crops and their wild hybrids
Reciprocal transplant experiments
Used mostly to examine “local adaption”. If a population is adapted to local/home conditions, if some of these individuals are transplanted into an “alien” habitat to which they are not adapted will show reduced survival, growth and/or reproduction relative to their natural home performance.
Adaption
A process that results from the effect of natural selection in a phenotype pool.
- reveal adaptive evolution by natural selection- population specific result -pg 68
- character adaptions- adaption refers to a trait that improves the fitness of individuals that have it relative to other that do not.
Genetic drift
Changes in genes or alleles do to something random. Has nothing to do with natural selection. Random chance fluctuations in a gene pool. Results in reduction of genetic variation (genetic erosion). Ex: migration
Also- bottleneck, founder effect and habitat fragmentation.
Gene flow
Migration of individuals/ genes in gamates, pollen, seeds between populations. Immigration into pop and emigration out of pop: changes the gene pool for both pops. Gene pools homogenize reduce likelihood of pop adaption.
- Size of migrant pop relative to recipient pop
- gene pool (allele freq) of migrant pop and how much it differed from the recipient pop
The demonstration of local adaption depends on:
- how env different are the habitats the source pops live in? The more diff the env the more different the selection pressures leading to adaption.
- how far apart or the transplant sites
- what is transplanted (seeds, seedling)?
- which env factors will be manipulated for investigation
- what kind of ecological data are measured? Focus on fitness
- what is the duration of the study?
