Biology 1620: First quiz

germ-line mutation

- A mutation that occurs in the egg and sperm or in the cells that give rise to these reproductive cells and therefore is passed on to the next generation

Scientific theory criteria: 2 and scientific theories are often comprised of two components, what are they?

1. Is not a guess 2. Explains a broad class of observations and is widely supported by evidence Scientific theories are often comprised of two components: 1. Pattern—observations about natural world 2. Process—mechanism that produces that pattern

Mutation is important in evolution: 3

1. Mutation is the ultimate source of genetic variation 2. Without mutations, evolution would eventually stop by maintaining genetic variation in populations 3. Mutation alone is usually inconsequential in changing allele frequencies at a particular gene

somatic mutation

A mutation that occurs in the somatic cells, will not affect the offspring of that individual

somatic cell

A nonreproductive cell, the most common type of cell in the body of a multicellular organism

• Geographic isolation occurs in one of two ways: Dispersal and Vicariance

A population moves to a new habitat, colonizes it, and founds a new population, the physical splitting of a habitat • A physical barrier splits a population into subgroups that are physically isolated from each other

population bottlenecks

A sudden decrease in population size in a large population. commonly caused by disease outbreaks and natural catastrophes

Lamarck's theory of evolution

Based on Aristotle's great chain of being • Organisms evolve by moving up the chain over time, evolution is progressive— producing larger, more complex or "better" species over time, the inheritance of acquired characteristics

Historical Constraints

Because all traits evolve from previously existing traits, adaptations are constrained by history • Not all traits are adaptive, and even adaptive traits are constrained by genetic and historical factors

artificial selection

Breeding organisms with specific traits in order to produce offspring with identical traits.

Mutation is the ultimate source of genetic variation (3):

Crossing over and independent assortment shuffle existing alleles into new combinations. Only mutation creates new alleles. Mutation just happens—not because organisms "want" or "need" it

transduction

DNA is transferred from a donor to a recipient cell by a virus

transfmoration

DNA relaeased into the envrionemnt by dead cells is taken up by recipient cell

Natural selection occurs in a wide variety of patterns or modes:

Directional selection • Stabilizing selection • Disruptive selection • Balancing selection

speciation

Disruptive selection, the formation of new species

typological thinking

Every organism was an example of a perfect essence, or type, were made in their current state • Types were essentially unchanging

• Researchers traditionally believed that speciation could not occur among sympatric populations because

Gene flow would overwhelm any differences among populations created by genetic drift and natural selection

At what level does natural selection operate?

Genes - alternative alleles • Individuals - alternative phenotypes (genotypes) • Groups - alternative populations

_______________ _____________ occurs during genetic bottlenecks and causes a change in allele frequencies

Genetic drift

What causes genetic drift in natural populations?

Genetic drift can be caused by any event or process that involves sampling error—not just sampling of gametes during fertilization or loss of individuals through accidents (founder effect and bottlenecks)

Prezygotic barriers

Habitat isolation • Temporal isolation • Behavioral isolation • Mechanical isolation • Gametic isolation

Balancing selection occurs when

Heterozygous individuals have higher fitness than homozygous individuals do—called heterozygote advantage • Consequence is that selection on different alleles is balanced • Genetic variation is maintained in the population 2. Certain alleles are favored at different times or in different places • Although allele frequencies change locally, overall genetic variation in the population is maintained. 3. Certain alleles are favored when they are rare but not when they are common

prezygotic barrier

Individuals of different species are prevented from mating successfully

disruptive selection

Intermediate phenotypes are selected against and extreme phenotypes are favored • Has the opposite effect of stabilizing selection • Increases variation in a trait

negative selection

Natural selection that decreases the frequency of a deleterious allele

positive selection

Natural selection that increases the frequency of an advantageous allele

Disadvantages of the Morphospecies Concept

One polymorphic species may be classified as more than one species • It cannot identify cryptic species that differ in non-morphological traits • The features used to distinguish species under this concept are subjective

inheritance of acquired characteristics

Parental traits are modified through use and then passed on

genetic bottlenecks

Population bottlenecks leads to this. —a sudden reduction in the number of alleles in a population

mechanisms that stop gene flow between populations are categorized into _____________ and _________________.

Prezygotic isolation, Postzygotic isolation

Postzygotic barriers

Reduced hybrid viability • Reduced hybrid fertility • Hybrid breakdown

Maintaining genetic variation is important

Selection can occur only if heritable variation exists in a population • Lack of variation can make populations less able to respond successfully to changes in the environment, and their average fitness will decline • If environmental change is severe, the population may become extinct

_______________ results from genetic isolation and genetic divergence. is a splitting event that creates two or more distinct species from an ancestral species

Speciation

phylogeny

The evolutionary history of a group of organisms

sympatric speciation

The formation of new species in populations that live in the same geographic area

Postzygotic isolation

The hybrid offspring do not survive or reproduce

germ cell

The reproductive cells that produce sperm or eggs and the cells that give rise to them

shared derived characteristics

Therefore, a species is defined as the smallest monophyletic group on the tree of life

Horizontal/Lateral gene transfer

Transfer of genes from one species to another

Morphospecies concept is widely applicable

Useful when there is no data on the extent of gene flow • Equally applicable to sexual, asexual, and fossil species

evolution

a change in the characteristics of a population over time

fitness trade-off

a compromise between traits, in terms of how those traits perform in the environment • Because selection acts on many traits at once, every adaptation is a compromise

A phylogenetic tree shows _______________________________ _________________________________________________________________

a hypothesized evolutionary history of living organisms

ecological species concept

a species is a set of organisms that is adapted to a particular set of resources (niche) in the environment.This explains differences in form and behavior between species as adaptations to resource availability

adaptation occurs when the __________ _______________ in a population change in response to natural selection

allele frequencies

Evolution is a change in ___________ _________________ of a population over time.

allele frequency

Speciation that begins with geographic isolation

allopatric speciation

genetic drift

any change in allele frequencies in a population due to chance (known in statistics as sampling error). • It causes allele frequencies to drift up and down randomly over time. It is especially prevalent in small populations. Changes in allele frequency are not adaptive

Sympatric Speciation by Polyploidization

autopolyploidy, self-fertilization, offspring. or allopolyploidy: sterile offspring/error in mitosis prior to meiosis so that meiosis proceeds nad then self-fertilization --> allopolyploid offspring

Evolution by natural selection is one of the _____ supported and most ______________ theories in modern biology

best, important

Genetic drift

causes allele frequencies to change randomly

Directional selection

changes the average phenotype in the population in one direction, tends to reduce the genetic diversity of populations

monophyletic group

consists of an ancestral population plus all of its descendants

Individuals with self-sacrificing alleles ___ or ____________ _____________ _____________>

die, produce fewer offspring

founder effects

event occurs when a group of individuals establishes a new population in a new area. Allele frequencies likely differ from the source population if the new population is small enough. This change in allele frequencies. especially common in the colonization of isolated habitats like islands.

Genetic drift is random with respect to _______________.

fitness

Some mutations are not in coding regions but can still affect phenotype by affecting ______________ _____________________.

gene expression

Natural selection is not the only mechanism of evolution and each process has a different affect on the _________ _______________ and _____________________________.

genetic diversity, fitness of a population

homozygous

genotype in which both alleles for a given gene are of the same type

heterozygous

genotype in which the two alleles for a given gene are different

Phylogenetic Species Concept

identifies species based on evolutionary history

No matter how natural selection occurs, it ____________ fitness and leads to adaptation

incraases

morphospecies concept

individual lineages differ in size, shape, or other morphological feature • Distinguishing features most likely arise if populations are independent and isolated from gene flow

vestigial trait

is a reduced or incompletely developed structure that has no (or reduced) function • Clearly similar to functioning organs or structures in closely related species

The decline of gene flow between ___________ ___________ _______________ is well documented. Isolating events include ____________ _______________>

isolated wild populations, habitat fragmentation

how does natural selection drive sympatric speciation

it can have the two extremes be more popular, and then once it gets strong enough (disruptive selection) then sympatic speciation occurs

mutations

modifies allele frequencies by continually introducing new alleles

why do adaptations occur

mutation, new source of allele, chance. loss of trait, no such thing as higher/lower organism

mutations can have different impact on fit: deletrious

mutations decrease the fitness of the organism Tend to be eliminated by purifying selection

• Mutations can have different impacts on fit: neutral

mutations do not affect an organism's fitness Occurs when a point mutation does not change the amino acid sequence

mutations do not affect an organism's fitness: beneficial

mutations increase the fitness—ability to survive and reproduce—of an organism Should increase in frequency in a population due to natural selection

Darwin and Wallace

natural selection

Most point mutations are ________ or ______________

neutral, deleterious

Mutation restores genetic diversity by creating _______ ________________, not only new combinations of alleles

new alleles

Thus, it is _____ possible for self-sacrificing alleles to persist by natural selection [we will discuss the evolution of cooperation later]

not

bottlenecks

occur when resources reach full capacity and cannot handle any additional demands; they limit throughput and impede operations

Gene flow

occurs when individuals leave one population, join another, and breed

allopatry

population or species that is physically isolated from other similar groups by an extrinsic barrier to dispersal

• Genetic isolation happens when ______________ __________________________ ________________________________.

populations become geographically separated

allopatry

populations that live in different areas

Descendent with modification

principle that each living species has descended, with changes, from other species over time

Genetic drift is _____________ with respect to fitness

random

stabilizing selection

reduces genetic variation in a trait but does not change average value of a trait over time - Reduces both extremes in a population = Favors intermediate phenotypes

___________ is always occurring at all levels and usually in the same direction The important and interesting cases are when _______ (same word) operates in different directions at different levels.

selection

As a result, ___________ ____________ increase in frequency while self-sacrificing alleles decrease in frequency

selfish allele

Individuals with ________, __________ alleles survive and produce more offspring

selfish, cheater

are all traits from evolution good?

some cannot be optimized due to fitness and trade-offs, some traits are limited by genetic, historical, or environmental constraints

Frequency-dependent selection

the fitness of a phenotype depends on how common it is in the population

biological species concept

the main criterion for identifying species is reproductive isolation

gene flow

the movement of alleles between populations • Occurs when individuals leave one population, join another, and breed. Gene flow equalizes allele frequencies between the source and recipient populations • Gene flow homogenizes allele frequencies among populations • In other words, movement of alleles between populations always tends to reduce their genetic differences

Horizontal/lateral gene transfer

the transfer of genetic material between organisms that are not parent and offspring

Natural selection acts on pre-existing ______________ among individuals

variation

population thinking

variation among individuals in a population was the key to understanding the nature of species

balancing selection

—occurs when no single allele has a distinct advantage • There is a balance among several alleles in terms of their fitness and frequency

genetic variation

—the number and relative frequency of alleles that are present in a particular population

natural selection

• Does not follow a linear, progressive pattern • Is based on variation among individuals in populations • Individuals with certain traits produce more offspring than others without these traits, population thinking, descent with modification

Sexual selection is a form of natural selection, which occurs when (2)

• Females choose certain males, and/or • Males compete among themselves to secure mates

phylogenetic tree

• Is a graphical summary of this history • Shows evolutionary relationships among genes, species and higher taxa

Acclimatization

• Occurs when an individual's phenotype changes in response to changes in the environment • The individual's genotype remains fixed • The changes are not passed on to offspring, because no alleles have changed

sympatry

• Populations or species that live in the same geographic area—close enough to interbreed