Evolution

Evolution Review Power PointThe purpose of this presentation is to provide a basic overview of the concepts of evolution.

The topics for review were taken directly from the Biology Keystone Assessment Anchors and Eligible content. Content for this lesson was derived from online sources and the Pearson, Prentice Hall Biology: Exploring Life book (pages listed correspond to this book)

You are NOT required to review this presentation we just felt it would be helpful for those who were not taught this information or who need a review.EvolutionMechanisms and EvidenceChapters 14.2, 14.4, 15.1, 15.2, 15.3 Pages 299-304, 314-315, 310-316, & 324-340ObjectivesExplain how natural selection can impact allele frequencies of a population

Describe the factors that can contribute to the development of new species (e.g., isolating mechanisms, genetic drift, founder effect, migration).

Explain how genetic mutations may result in genotypic and phenotypic variations within a population.

Interpret evidence supporting the theory of evolution (i.e., fossil, anatomical, physiological, embryological, biochemical, and universal genetic code).

Distinguish between the scientific terms: hypothesis, inference, law, theory, principle, fact, and observation.

Populations and Gene PoolsA biological population is a local group of individuals belonging to the same species

Smallest level at which evolution can occur

Individuals and EvolutionNatural selection acts on individuals AND affects reproductive success

Natural selection ONLY becomes clear when an entire population is tracked over timeEvolutions of PopulationsGene pool - all of the alleles in all the individuals that make up a population

Reservoir from which the next generation draws its genes..where genetic variation (raw material of evolution) is stored. Changes in Gene PoolsMutations & sexual recombination lead to genetic variation.& are RANDOM

Natural selection (evolution) is NOT random

Environment favors genetic combinations that increase survival and reproductive successChanges in Gene PoolsSome alleles may become more common in the gene pool

Change in frequency of alleles

Usually expressed as decimal or percentageChanges in Gene PoolsBe the bird eat the bug Activity shows how allele frequencies change overtime

http://www.nhm.ac.uk/nature-online/evolution/what-is-evolution/natural-selection-game/the-evolution-experience.htmlChanges in Gene PoolsMicroevolution evolution on the smallest scale a generation-to-generation change in the frequencies of alleles within a population.

Evolution based on genetic changesChanges in Gene PoolsPopulations that do not undergo change to their gene pools are not presently evolving.. Hardy-Weinberg equilibrium

Frequency of alleles in that gene pool are constant over time.

Natural populations dont stay in this for longGenetic DriftGenetic drift change in the gene pool of a population due to chance.

All populations subject to some

Smaller populations are impacted more by genetic drift.in smaller populations allele frequencies can vary from one generation to the nextGenetic Drift Bottleneck EffectGenetic variation in a population decreases significantly due to a drastic reduction of population size (and gene pool).

Genetic Drift Bottleneck EffectMay be due to disasters (earthquakes, floods, droughts, and fires)

Could reduce the ability of population to adapt to environmental changeGenetic Drift Founder EffectChange relates to genetic makeup of the founders of the colony

A few individuals colonize a new habitat (isolated island, lake, etc.)

Smaller colony, less genetic makeup diversity than that of the larger population

Chance reduces genetic variation

Finches of Galapagos IslandsGene flowGene flow exchange of genes between populations

Occurs when fertile individuals (or gametes) migrate between populations

Reduces genetic differences between populations.

Can mix neighboring pops into a single pop w/common gene poolMutation p.314Natural selection, genetic drift, or both can influence whether the frequency of a new mutation increases in a population

If mutation is beneficial allele increasesIf mutation is harmful allele decreases MutationKey role in evolution as the original source of genetic variation that is the raw material for natural selection.

Esp important as a source of variation in asexually reproducing organisms (bacteria)

In sexually reproducing organisms variation is mostly due to scrambling of existing allelesGenetic drift, gene flow, and mutation can cause microevolution (changes in allele frequencies)

Do NOT necessarily lead to adaptationNatural Selection and Fitness p.314-315Natural selection = blend of chance and sorting

Chance from mutation and sexual recombination of alleles -> genetic variationRANDOM

Sorting accomplished by differences in reproductive success NOT randomNatural Selection and FitnessFitness contribution that an individual makes to the gene pool of the next generation compared to the contributions of other individuals.

Individuals whom are more fit/healthy or well adapted to their environment are more likely to survive to pass on genes to offspring.

Speciation15.1 p. 324-330Speciation formation of new species

Development of New Species4 factors that lead to Speciation1. Behavioral/Reproductive Isolation

2. Geographic Isolation

3. Migration Genetic Drift Founder effectBehavioral Reproductive Isolationp. 325-326Timing different breeding seasons

Behavior - Two populations are capable of interbreeding, but they have different behaviors that prevent them from breeding.Behavioral Reproductive Isolationp. 325-326Habitat species adapted to different habitats in the same general area. Ex. one fish adapted to living along lake edge others to open water.

Others reproductive structures incompatible, reproductive facilitators (insects) may only frequent one species, zygote may fail to develop.Geographic Isolationp. 327-328Form of reproductive isolation in which two populations are separated physically.

Steps:1. Start with an interbreeding population of one species.

2. The population becomes divided by a physical barrier. This can happen when some of the population migrates or is dispersed, or when the geography changes catastrophically (e.g., earthquakes, volcanoes, floods) or gradually (erosion, continental drift).

3. The two populations can over time change relative to each other, because each population has slightly different gene pools (random), different environments with different food sources, shelter, predators, and each gene pool undergoes its own mutation and natural selection.

4. Even if the barrier is removed and the two populations meet again, they are now so different that they can no longer breed. They are reproductively isolated and are two distinct species.Geographic Isolationp. 327-328Examples:A pond dries up to make two ponds.A river is re-routed through a field.A new road goes up.A few seeds stuck on a birds feather fall on a new island.A flood washes a few lizards or insects to an island.Geographic Isolation

Development of New Species4 factors that lead to Speciation3.Migration: Movement of animals from one place to another. Changes the gene pool of a population when animals with different genes enter or leave.4.Genetic Drift: Random change in allele frequencies that occurs in small populations.Founder effect: Extreme example of genetic drift. Change in allele frequencies as a result of the migration of a small group in a population.

If a population begins with a few individualsand one or more carry a particular allelethat allele may come to be represented in many of the descendants.

Rate of SpeciationPunctuated Speciation evolutionary model suggesting species often diverge in spurts of relatively rapid change, followed by long periods of little change.

*NOTE: relatively rapid change here is referring to GEOLOGIC time. So these changes still take a very long time to occur if we were to measure this compared to a human life span.

Interpret evidence supporting the theory of evolution (i.e., fossil, anatomical, physiological, embryological, biochemical, and universal genetic code).

Fossil14.2 p 299-30015.3Fossils typically form in sedimentary rock

Oldest layers tend to be at the bottom of a series of bands of rock and therefore oldest organisms are typically found in the deepest (bottom) layers.

Fossil14.2 p 299-30015.3Fossil evidence shows that ancient whales evolved from ancestors with hind limbs.

Whales today have the remains of what appear to be hipbones but do not have hind limbs. Fossil14.2 p 299-30015.3Fossils provide scientists with information about ancient animals structures, behaviors, feeding patterns, etc.

Within the fossil record scientists have found evidence of organisms changing over time.Anatomical and Physiological 14.2 p. 301Homologous structures similar structure found in more than one species that share a common ancestor

The front limbs of primates, cats, whales, and bats all have similar arrangements of bones even though they each use these front limbs in different ways. Anatomical and Physiological 14.2 p. 301Vestigial structures remnant of a structure that may have had an important function in a species ancestors, but has no clear function in the modern species.

Ex. Whales today have small vestigial hipbones but lack hind legs Embryological14.2 p. 30215.2 p. 333Embryos of closely related organisms often have similar stages in developmentBiochemical and Universal Genetic Code14.2 p. 303Siblings have similar DNA and protein sequences

Sequences of unrelated individuals of the same species show more differences

Likewise, species with similar DNA and protein sequences probably had a common ancestor

The greater the number of differences the less likely they are to share a close common ancestorDistinguish between the scientific termsHypothesis suggested, testable answer to a well-defined scientific question

Inference logical conclusion based on observations

Distinguish between the scientific termsLaw governs a single action or situation, generalizes observations made about that action or situation

Theory explanation of an entire group of phenomena (much more broad, complex, and dynamic); explains many related observations and is well supported by scientific evidence

Distinguish between the scientific termsLaw a descriptive statement or equation that reliably predicts events under certain conditions

Theory well-tested explanation that makes sense of a great variety of scientific observations

Principle a rule or law concerning a natural phenomenon or the function of a complex system; the principle of the conservation of mass - http://dictionary.kids.net.au/word/principle

Distinguish between the scientific termsFact a reality or truth

Observation use of the senses to gather and record information about structures or processes in nature