Bio Unit 9 Evolution, Population Genetics, Phylogeny and Systematics

Ingroup

organisms that share characteristics

Explain the specific inferences Darwin drew from these observations

Individuals better suited to environment have a greater chance of surviving and reproducing Populations will accumulate favorable traits over generations

Explain how intrasexual and intersexual selection can lead to sexual dimorphism

Intrasexual selection: what enables individuals to outperform to get mate gets passed on Intersexual selection: character that females look for will be passed down

Population

A group of individuals of the same species who live in the same area and interbreed, creating fertile offspring.

State the basic observations Darwin used to support his theory of natural selection

1. Variation within a population 2. Traits can be inherited 3. More offspring produced than an environment could support 4. Many offspring do not survive 5. Individuals that are better suited to the environment are more likely to be the ones that are going to reproduce (and survive)

autopolyploidy

A diploid cell after going through mitosis does not go through cytokinesis. It therefore has 4 of each chromosome when it should just have 2. Then when it goes through meiosis, the two cells it produces are both diploid (2 of each chromosome). When two of those cells join together they produce a cell that is tetraploid.

Sympatric speciation

A subset of a population forms a new species without geographic isolation (new species arises in same geographic area as parent species_

Postzygotic Barriers

After fertilization Reduced hybrid viability- offspring don't survive well/long enough to reproduce. Mortality in embryonic development or sickly young Reduced hybrid fertility- offspring/hybrids cannot reproduce Hybrid breakdown- offspring is viable and fertile but when hybrid reproduces with either of parent species, second generation offspring have reduced viability or fertility

Explain how sympatric speciation can occur (we discussed 3 possibilities)

Autopolyploidy Allopolyploidy Habitat differentiation Different individuals in a species prefer different part of habitat Living on different part of island, same population Sexual selection: a form of natural selection in which individuals with certain traits are more likely to obtain mates

Define species using the biological species concept

Biological species concept : a species is a population or group of populations whose offspring, when they interbreed, have the potential to produce viable(alive), fertile (can reproduce) offspring. This can be problematic because of hybridization. There is no way to determine whether organisms that are only in the fossil record were once able to interbreed, and this info is also useless for organisms that produce asexually

Explain how classification and phylogeny are linked

Classification requires the use of phylogeny Phylogenetic trees illustrate the connection between classification and phylogeny

Explain how genetic variation is preserved in a population

Diploidy: recessive alleles can be hidden but appear in later generations Balancing selection occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population Heterozygote advantage is a type of balancing selection in which heterozygous individuals have greater reproductive success than either type of homozygote, two or more alleles for a gene are maintained in the population Frequency-dependent selection is a type of balancing selection that maintains two different phenotypic forms in a population Frequency-dependent selection keeps each phenotype close to 50% Neutral Variation -- does not affect fitness, reproductive success, traits that have nothing to do with natural selection Changing environment

Microevolution

Evolutionary change at the population level is called microevolution. It is the change in allele frequencies over generations

Explain how natural selection can lead to the evolution of complex structures

Evolutionary novelty can arise when structures that originally played one role gradually acquire a different one. Natural selection cannot predict the future; it can only improve an existing structure in the context of its current use. Novel features can arise gradually via a series of intermediate stages, each of which has some function in the organism's current situation. Complex structures may evolve in stages from simpler versions with the same basic function. The species that generate the greatest number of new species determine the direction of major evolutionary trends. Evolutionary trend does not imply that evolution progresses toward a particular goal. Evolution is the result of interactions between organisms and the current environment.

List the 5 requirements for the Hardy-Weinberg Theorem

Extremely large population size in order to combat genetic drift No gene flow No mutations which means no new alleles Random mating which means no sexual selection, which means that there are no favorable characters...part of natural selection No natural selection

List examples of direct observations of evolutionary change

Finches in the golápagos islands developed smaller beak depths for eating small seeds that became abundant during wet years. There is an evolution of pesticide resistant insect species. Now pesticides are less and less effective because over generations the insects develop an allele that allows them to survive the effects of the pesticides which eventually creates a pesticide-resistant population Some mosquitoes that were sprayed with DDT carried an allele that codes for an enzyme that detoxifies the pesticide DDT.

Explain how both rapid and slow speciation tempo can be valid

Fossil record shows both occurring

Compare/contrast the two models for the tempo of speciation.

Gradualism is based on very minute changes over long periods of time create major changes. In contrast, Punctuated equilibrium is based on rapid changes with longer periods of genetic stability.

Taxonomy

How organisms are named and classified How we name and classify (based on systematics) → systems give us evolutionary history (phylogeny)

Determine circumstances in which each species concept could be useful

Morphological species concept can be applied to asexual organisms and fossils and does not require information on possible interbreeding Ecological species concept. Two species of fish may be similar in appearance but distinguishable based on other factors Phylogenetic species concept. Biologists can trace the phylogenetic history of species and can distinguish groups that are generally similar yet different enough to be considered separate species

Identify and define other species concepts and state why more than one concept can be useful

Morphological species concept's advantages are that it can be applied to asexual organisms and fossils and does not require information on possible interbreeding Look alike: Body shape and other structural features Ecological species concept focuses on unique adaptations to particular roles in a biological community or ecosystem Phylogenetic species concept defines a species as the smallest group of individuals that share a common ancestor and thus form one branch on the tree of life Shared genetic history

State the three major factors that can alter allele frequencies in a population

Natural Selection Genetic Drift Gene flow

Explain how the major factors (including subgroups) can change allele frequencies in a population

Natural selection Populations consist of varied individuals, and some variants leave more offspring than others. By consistently favoring some alleles over others, natural selection improves the match between organisms and their environment. Genetic Drift Chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next → can lead to loss of genetic variation An allele can be lost from a small population by such chance fluctuations. Or cause harmful alleles to become fixed Bottleneck effect: Catastrophes such as hurricanes, floods, or fires may kill large number of individuals, leaving small surviving population that is unlikely to have the same genetic makeup as the original population Analogous to shaking just a few marbles through a bottleneck, certain alleles may be present at higher frequency in the surviving population than in the original population, others may be present at lower frequency, and some may not be present at all Genetic drift as a result of bottleneck reduces the genetic variation of the population and may increase the frequency of harmful alleles Founder effect: few individuals colonize an island or other new habitat The smaller the group, the less likely that the genetic makeup of the colonists will represent the gene pool of the larger population they left Gene flow A population may gain or lose alleles when fertile individuals move into/out of a population or when gametes (like plant pollen) are transferred btw. populations Genetic drift, gene flow, and mutation can cause microevolution. Only by chance can they improve a population's fitness. Also, Process of natural selection, where better-adapted individuals are more likely to survive and reproduce, is not random (Only natural selection consistently leads to adaptive evolution)

From where do all new alleles arise?

New alleles come from genetic mutations....changes in the nucleotide sequence of DNA Serves as raw material for evolution Changes in the nucleotide sequence of DNA - most of the time they are bad, but they can sometimes be good (always accidental)

Explain why no population fits the Hardy-Weinberg Theorem

No population fits the Hardy-Weinberg Theorem because no population can remain that consistent. In a population there are always members that will leave and new ones will enter. In an environment there will always be certain characteristics that are more favorable than others. There is no way to completely and entirely prevent genetic mutations.

complete dominance

One allele is completely dominant over the other

Homology

People have characteristic that are similar because of a common ancestor There is anatomical homology and molecular homology. Anatomical is similar visual characteristics, and molecular is internal.

Explain the purpose of a phylogenetic tree; explain the significance of a branch point in a phylogenetic tree

Phylogenetic trees explain/depict hypothesis of the evolutionary history of a species The branching points show common characteristics/ancestors and reflects the similarities between organisms Phylogenetic trees represent the evolutionary history of an organism on group of organisms Demonstrate patterns of descent not phenotypic similarity Sequence or branching does not necessarily indicate actual age of the particular species Do not assume one group evolved from the group next to it Phylogenies are decided with anatomical or molecular homologies

Prezygotic Barriers

Prevent fertilization Habitat isolation-not in same location (lack of opportunities to encounter) Temporal isolation- breeding at diff times, mating seasons, night and day Behavioral isolation- different mating behavior. If mating dances are different, don't recognize signals Mechanical isolation- physical incompatibility of reproductive parts (parts don't fit together) Gametic isolation- on outside of egg, certain proteins to attract sperm. only fertilized if in same species. molecular incompatibility of eggs and sperm / pollen and stigma.

Define fitness

Relative fitness is the contribution an indivudual makes to the gene pool of the next generation, relative to the contributions of other individuals in that population Those who make a larger contribution to the next generation are more fit in comparison to those who make a smaller contribution The fittest individuals are those that produce the largest number of viable, fertile offspring. The pass on the most genes to the next generation. Related to natural selection because they are the "fittest" Being "fit" Depends on the phenotypes of the individual and how they interact with their environment

Explain why natural selection cannot create perfect organisms (and, of course, there is no such thing as "perfect!")

Selection can act only on existing variation. Natural selection favors only the fittests variants from the phenotypes that are available, which may not be the ideal traits. New, advantageous alleles do not arise on demand. Evolution is limited by historical constraints. It does not build each new complex structure from scratch; it co-opts existing structures and adapts them to new situations. Adaptations are often compromises. A blue-footed booby uses its webbed feet to swim after prey in the ocean, but these same feet make for clumsy travel on land. Chance, natural selection, and the environment interact. Chance events often affect the genetic makeup of populations. When a storm blows insects over an ocean to an island, the wind does not necessarily transport the individuals that are best suited to the new environment. In small populations, genetic drift can result in the loss of beneficial alleles. In addition, the environment may change unpredictably from year to year.

Explain how sexual reproduction increases the genetic variation in a population

Sexual reproduction rearranges alleles into new combinations Crossing over : during meiosis, pairs of homologous trade pieces of genetic info by crossing over Independent assortment : homologous chromosomes separate into gametes independently of the other chromosome pairs Random fertilization : each zygote made by a mating pair has a unique assortment of alleles resulting from the random union of sperm and egg

Explain potential circumstances where each of the three modes of selection could occur

Stabilizing selection: Environment where medium coat color helps camouflage. Mice with very white or very dark coats will be taken out. Directional selection: Environment where dark OR light coat color helps camouflage. The lighter/darker and middle are easier to spot, so that phenotype is selected Disruptive selection: Environment where dark AND light coat color helps camouflage. Environment has two types or rock: light and dark; mice can camouflage in either place

Explain what the Hardy-Weinberg Theorem tells us

The Hardy-Weinberg Theorem tells us that there is no change in allele or genotype frequencies from one generation to the next. In order for a situation to be a hardy-weinberg equilibrium there must be no changes in frequencies from generation to generation.

Phylogeny

The evolutionary history of a species or group of species Fossil record provides substantial chronicle of evolutionary change that can help trace the phylogeny of many groups Can also be inferred from morphological and molecular homologies among living organisms

Explain how the fossil record supports Darwin's theory of evolution

The fossil record is the chronological evolution of organism of over millions of years. Fossils are engraved in geologic time in the order in which fossils appear in the rock strata (layers of rock). The fossil record provides us with ancestors for currently living species, as well as species that no longer exist and have no descendants. Darwin predicted by the existence of fossils that there were transitional forms that linked very different groups of organisms Example : whales evolved from land-dwelling mammals....and if so fossils would show a series of changes in the lineage of mammals that eventually turned into aquatic animals. Thousands of fossil discoveries have since shed light on the evolutionary origins of many groups of plants and animals

Explain the phrase "descent with modification"

The phrase descent with modification was Darwin's phrase to describe evolution. He believed that species that we see today are descendants of ancient ancestors, but that they still resemble these ancestors in some ways with certain characteristics. Differences gradually accumulated in a process called descent with modification. Things will be inherited from generation to generation, but certain things will also change.

incomplete dominance

There is a phenotypic difference between the homozygotes and the heterozygotes.

Allopatric speciation

When population of one species becomes isolated geographically new species arises in different geographic area as parent species A mountain range may emerge and gradually split a population or organisms that can inhabit only lowlands A large lake may subside until there are several smaller lakes, isolating certain fish populations can also occur when individuals colonize a remote area and become geographically isolated from the parent population

Allopolyploidy

When two different species combine. The initial resulting hybrid is sterile, however it goes through asexual reproduction. After going through mitosis, again it does not go through cytokinesis. The resulting hybrid species is diploid and can reproduce sexually.

Sexual selection

a form of natural selection in which individuals with certain traits are more likely than other individuals to obtain mates

Convergent evolution

a process where species from different evolutionary branches may come to resemble one another if they live in similar environments and natural selection has favored similar adaptations

Adaptation

an inherited character that enhances an organism's ability to survive and reproduce in a particular environment Adaptations are basically the accumulation of a variety of modifications in a species that better fit their way of live in their environments

Binomial nomenclature

assigned 2-part scientific name to each species (avoid confusion) The first part is the genus - a group of closely related species The second part, the specific epithet, is used to distinguish species within a genus

codominance

both alleles are equally expressed in heterozygotes.

Hierarchical classification

classification levels are generally defined by morphological characters chosen by taxonomists rather than by quantitative measurements

Systematic

classifying organisms and determining their evolutionary relationships

macroevolution

evolutionary change at the species level Major events in the history of live on earth

Sexual dimorphism

differences in appearances, sexual characteristics, noticeable differences not directly associated with reproduction or survival; often manifested in a size difference, but it can also include forms of adornment, such as manes on lions or colorful plumage on birds

dominant vs. recessive

dominant: allele that is fully expressed in the phenotype of a heterozygote recessive: allele whose phenotype is not observed in a heterozygote

Ancestral character

everyone in the ingroup shares this character

Maximum parsimony

fewest evolutionary events or the fewest DNA nucleotide changes Things that are the most closely related have the fewest evolutionary events or the fewest DNA nucleotide changes

gene vs. allele

gene: sequence of DNA that codes for a particular trait allele: sequence of DNA that codes for a particular character

Explain how one can try to differentiate between analogy and homology

homology- similar origin analogy- similar function

Intrasexual selection

individuals compete directly with members of the same sex for mates

Intersexual selection

individuals of one sex are choosy in selecting their mates Males with the largest or most colorful adornments are often the most attractive to females Every time a female chooses a mate based on a certain appearance or behavior, she perpetuates the alleles that influenced her to make that choice and allows a male with that particular phenotype to perpetuate his alleles Advantage to females being choosy is that females prefer male traits that are correlated with "good genes"

Shared derived character

only certain members in the ingroup have these characters

Purpose of postzygotic Barriers

occur after zygote forms

Fixed allele

only allele in population → offspring cannot have anything but that allele.

Genotype frequency

out of all the genotypes in a population, the percentage that one genotype appears

Write the equations that define the Hardy-Weinberg Theorem; use these equations to solve problems

p+q = 1 p=frequency of dominant allele, q=frequency of recessive allele p^2 + 2pq + q^2 = 1 p2 is homozygous dominant, 2pq is heterozygote, q2 is homozygous recessive

phenotype

physical and physiological features of an organism

Purpose of prezygotic Barriers

prevent mating or fertilization between species (before zygote forms)

Reproductive isolation

prevents genetic exchange and maintains a boundary between species

Explain the gradualism model and the punctuated equilibrium model for the tempo of speciation

punctuated equilibrium: Paleontologists coined the term punctuated equilibria to describe these long periods of little apparent morphological change (equilibria) interrupted (punctuated) by relatively brief periods of sudden change gradualism: Other fossils species appear to have diverged gradually over long periods of time. Differences gradually accumulate, and new species evolve gradually from the ancestral population

Maximum likelihood

the most likely sequence of evolutionary events when following certain rules about how DNA changes over time

Biogeography

species that are similar to each other live near each other

genetic variation

the differences among individuals in the composition of their genes.

genotype

the genetic makeup of an organism

Outgroup

the organism that shares no common characteristics/least number of common characteristics

Allele frequency

the percentage of all the alleles in a population that are one specific allele

Natural selection

the process by which individuals with certain, more desirable, characteristics are more likely to reproduce and survive than the individuals without the trait Although natural selection happens through interactions between individual organisms and the environment, the individuals themselves don't evolve, but rather the population evolves over time Natural selection can amplify or diminish only heritable traits. Acquired characteristics can't be passed onto offspring because they aren't coded in the genes of the organism's gametes. Evolution is not goal directed; it does not lead to perfectly adapted organisms like artificial selection does

Speciation

the process by which one species splits into two or more species Every time speciation occurs the diversity of life increases because there are now more species (appearance of new species) Ancestral species give rise to more species which then branch off to new lineages and then again and again When one species splits into two, the new species share many characteristics because they come from a common ancestor

Artificial selection

the selective breeding of domesticated plants and animals in order to produce the occurrence of desirable traits in the offspring If you wanted your dog to have a certain color coat you could selectively breed the dogs in order to reproduce the desired characteristic

Analogy

this is convergent evolution....organisms have analogous anatomical structures. They externally look similar, but internally/molecularly they are different This comes from evolving in similar environments, but it is not from ancestry Analogous features share similar functions but not common ancestry Analogous organisms could externally look very similar to each other but internally are very very different. (example = the moles that were mammals but the others that were marsupials)

Gene pool

which alleles are present in the population