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UTC / Biology / BIOL 3350 / How can natural selection lead to evolution?

How can natural selection lead to evolution?

How can natural selection lead to evolution?


School: University of Tennessee - Chattanooga
Department: Biology
Course: Evolution
Professor: Oneil
Term: Spring 2015
Tags: evolution, Adaptation, and Naturalselection
Cost: 50
Name: Evolution Exam 1 Study Guide
Description: Hello class! These notes include content from chapters 1-4. With these notes and a basic understanding of the Hardy-Weinberg equation, you should be set for this Friday's exam!
Uploaded: 09/18/2017
7 Pages 69 Views 2 Unlocks


How can natural selection lead to evolution?

1 Study Guide

Scientific Method: 1 Making an observation 2 Identifying Critical questions

3 Generating Hypotheses (4 Making testable predictions (5 Making observations and performing experiments.

Gathering and analyzing data

Interpreting results and drewing conclusions. Hypothesis- A tentative explanation, that can be tested. A good

What are the factors that limit adaptation?

- hypothesis is based on previous research is repeatably

and can be proven wrong. Experiment. The best way to test a hypothesis. Must have We also discuss several other topics like What were the three reasons for egypt's art reaming the same all those years?

It control group and It experimental group, and the control & experimental groups should be carefully

controlled, randomized, and should only differ in

Why not a variation in genes doesn't always produce a variation in fitness?

one way by the variable that is being studied. * Be critical of scientific studies. Could have alternative explanations, etc. Correlational Study Examines how two variables are related, but

I cannot infer causation. A strong positive or

negative correlation could mean that the variables We also discuss several other topics like Who believed that the brain must be mapped, meaning the movement of hands will be localized in one part of the brain?

are somehow linked. ☆ Replication is very important for both experiments and correlation studies. Theory A comprehensive explanation of some aspect of nature that is

- supported by a vast body of evidence Evolution - Change in allele frequency through time, generation after We also discuss several other topics like How many base pairs of dna polymerases have a significant human genome?
Don't forget about the age old question of What is the meaning of domination of crete?

o generation, in populations. Allele-One of 2t versions of a gere found at the same place on a chromosome.

Gene- Unit of heretitary into, a segment of DNA. Heritable Variation - Differences in traits between individuals that are determined

by aqres and can be passed from parent to offspring. Reproductive Success-Number of offspring produced in some given time Fitness- Relative Lifetime Reproductive Success. How many offspring We also discuss several other topics like Who is antonio damasio?

compared to others in the population


* Aim of Evolutionary Biology: Understand diversity of life. Microevolution Short timescale (relatively), and on the population We also discuss several other topics like Why settlements are created?

level. How alleles & frequencies charge in a population,

how traits become adaptations. Macroevolution - long time scate, across populations. Fossil history,

a systematics, studying the processes that produced life

diversity now and the throughout fossil records. To know whether evolution occured, changes in allele frequencies in

a population across generations must be measurable. Mechanisms of Evolution 1 Genetic Drift - Random changes in allele frequency across generations

due to chance events & Alleres can be elinitaated, or their numbers just increase/ decrease. Has

a larger effect on smaller populations. 2 Migration Movement of individuals into or out of the population.

Can change allele frequencies, gain new alleles, or eliminate an allele. 3 Mutation ' A change in DNĄ. *Can change allele frequencies, gain new alleles, or eliminate an allele. 4 Natural Selection - Occurs when there is a relationship between a trait

and reproductive success. But, evolution might not occur. Mutation and Migration can increase genetic variation in a population because they can introduce new alleles. This variation is essential

for genetic evolutionary change to occur! However, Selection leads to some individuals having greater reproductive

Success because of their phenotype How can Natural Selection lead to Evolution?

There must be variation in a trait. 2 There must be differential reproduction - because of that trait,

limited resources lead to not all individuals reproducing to full potential. 13 The trait in question must be heritable with a genetic basis.

* End result adaptation


Adaption- Characteristics that enhance an organisms' reproductive success in

a particular environment. @ Phenomenon of an organism being well-suited to its environment.

The process by which organisms became well-suited to their environment. * Evolution by natural selection is a form of adaptive evoltion & Selection gets on individuals, but evolution acts on populations. Evolution

does not always lead to evolution Phylogenctics - Involved with macro evolution, reconstruction of the

evolutionary history of species. Speciation - Process by which new species originate and remain separate * Over time, enough changes can occur & accumulate into distinct species.

Evolution can happes quickly, speciation takes time. But with the creation

of a new species, the old species still exists usually Adaptive Evolution * Natural Selection causes adaptive change in traits and genes. Adaptive

evolution is driven by natural selection. On the flipsicle, neutural evolution causes non-adaptive charges

in traits & genes Conditions Necessary For Either Adaptive or Nectural Evolution: 10 Variation in individuals in lifetime a reproductive success.

2 Heritable Variation in a trait.

Contidian Necessary for Adaptive Evolution: (3) Trait of interest must be correlated with reproductive success.









e Genetic Drift

& Ecology quarantees variation in Lifetime Reproductive success, because

resources are linited and some individuals aquire resources better

than others because of their phenotypes. * There will be no evolutionary change in atrait that has no heritable - variation, however, almost all traits have some heritable variation

Heritable Variation- Differences in traits between individuals that can

be passed from parent to offspring. A there is no acarimera Conscious goal to natural selection, nothing is

trying to make a perfect organism? & What is adaptive now might not be adaptive later or in a different

environment Factors that linit Adaptation

Gene Flow- When an organish born in one environment reproduces somewhere

else, so geres that are successful in one place may end up in

individuals living in a place where the traits we no longer

useful. & Kinda hand-in-hand with migration. Can lead to maladaptation, but

not always. 12 Adaption takes time. However, strong selection can lead to rupid

I adaptation 3 Tradeoffs- When a change in one trait that leads to increased

- reproductive Sucess is linked to a trait with decreased reproductive success. * If trade offs didn't exist, traits would be driven to the extreme (4 Natural constraints limit the response to selection. There is a natural

limit to things such as size, mass, what DNA can control, history,

chemistry, physics, physiology, etc It is possible for past adaptations to become future constraints! ☆ No evolution for the good of the species at the expense of the individual,

this is not how selection works. Compassion has a basis in individual benefits!



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Direct Fitness-Total number of surviving offspring an individual produces Indirect Fitness- Total number of offspring that a relative produces because

of an individual, weighted by how related they are. Inclusive Fitness-Gerctic contribution to the next generation through

one's own reproduction & the portion of reproductive success

of relatives caused by that inclivichels contribution Direct Fitness & Indirect Fitness = Inclusive Fitness Nectural Evolution

A variation in genes doesn't always produce avariation in fitness. t why not?

Some genetic variation does not affect protein creation. Genetic code is redundant, and hom differences in nucleotides might produce the

same amino acids. 2. Changes in amino acids may not change a protain's function. 13 Genes affecting a canalized trait are nevtral when not expressed. Canalized Trait-Atrait with little phenotypic variation, even if geres

and environment differ wildly. 14 What is adaptive in one environment might be nectural in another.

☆ However, despite all of this ventural genetic variation can still lead to

evolutionary charge It How? 1 Mandelian Lottery- Genes get passed from parent to offspring - by

chance! Especially with a heterozygous parent. 13 Environment may influence number of offspring, not phenotypes alone 13 Founder Effect - New populations in new environments may be foundes

by a small number of individuals with a limited gene pool. As

time passes, original population & now population will have different

phenotypes. 4 Genetic Bottlenecking - When a catastrophy occurs, some may survive not

because of phenotype but of chance, creating smallergene pool. * All of these involve statistical random sampling, which then create a population

with fewer traits to draw from. Geretic Drift.

These tend to lead to an eventual fixation or loss of an allele, which reduces genetic variation within a population.

However, this also increases genetic variation across populations. Molecular Clock-A relatively consistent rate in which the nucleotide

a substitution for a particular gene happens. * It is unclear whether Genetic Drift causes most evolutionary

change or not. Population Genetics: Population Genetics - Used when the phenotype / genotype relationship is simple. a A simple way to approach simpler genetics. Sexual Reproduction - Genetic Material from two parents is mixed to

produce unique offspring, Asexual Reproduction. When a parent produces offering, usually identical

to them by splitting in halfor producing an infertilicedegge Sexual Reproduction liberates an allele from its current genetic context by giving it the the possibility of mixing with other allles from another

parent. This is not possible in Asexual reproduction * As a result, sexual reproduction is more likely to lead to the spread of

favorable alleles and the extermination of unfavorable alleles Haploid- An organism or cell with a single set of chromosomes. Diploid- An organism with 2 copies of chromosomes, one from each parent.

In diploids, an alleles rate of dominance affects its rate of change. & For example, In heterozygotes, the recessive allele cannot be selected

for or against, so the rate of spreading a favorable recessive allele and eliminating an unfavorable recessive allele is slower. However, favorable danirent alleles spread quickly and unfavorable dominant alleles are clininated quickly A Because haploids only have one version orf an allele, there is no possibility of a hidden recessive allele so evolutionary change happens

pretty quickly.



Quantitative Genetics Quantitative Genetics Used for traits with a continuous distribution of - phenotypes, and traits influenced by many genes. *Mendelian genetics cannot be used to explain the relationship

between genotype and phenotype.

Phenotypic variation results from genetic variation and environment. | P=G+E

If genes and environment aut indiependently, a researcher may trip to nullify one of these variables to quantify what is goretic

and what is environment, done through control. Variation (Phenotype) = Variation (Genetics) 7 Variation (Environment).

If phenotype variation is due to environment, selection won't lead to

large geretic changes in an environment If phenotypic variation is due to genetic variation, selection can

lead to large genetic change Heritability-ha - Additive genetic variance expressed as a fraction

of total phenotype. You can estimate heritability by calculating the slope of the relationship between parental and offspring trait..


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