Biology Chapter 13

Adaptation

Inherited traits that enhance an organism's ability to survive and reproduce in a particular environment

What does the founder effect explain?

It explains the relatively high frequency of certain inherited disorders among some human populations established by small numbers of colonists.

In what ways do we contribute to the problem of antibiotic resistance?

Livestock producers add antibiotics to animal feed as a growth promoter and to prevent illness

Two important points about natural selection

-More of an editing process than a creative mechanism -It is contingent on time and place where it favors heritable traits that fit the current, local environment

The three main causes of evolutionary change are

-Natural selection -Genetic drift -Gene flow

Chance, natural selection, and the environmental interact

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Three key points about evolution by natural selection

1. Although natural selection occurs through interactions between individual organisms and the environment, individuals do not evolve. It is the population or group of organisms that evolve over time as adaptive traits become more common in the group. 2. Natural selection can amplify or diminish only heritable traits 3.Evolution is not goal directed, it does not lead to perfectly adapted organisms. It is the result of environmental factors that vary in location and time

5 Conditions of Hardy-Weinberg Principle

1. Very large population- the smaller the population, the more likely that allele frequencies will fluctuate by chance from one generation to the next 2.No gene flow between populations- When individuals move into or out of populations, they add or remove alleles, altering the gene pool 3. No mutations- By changing alleles or deleting or duplicating genes, mutations modify the gene pool 4. Random mating- If individuals mate preferentially, such as with close relatives (inbreeding), random mixing of gametes does not occur, and genotype frequencies change 5. No natural selection- The unequal survival and reproductive success of individuals (natural selection) can alter allele frequencies

Sexual selection

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

MRSA

A formidable super bug known as methicillin-resistant Staphylococcus aureus can cause flesh-eating disease, and potentially fatal systemic (whole body infections).

Darwin's boldest hypothesis

All life-forms are related

Homologous structure

Anatomical similarities in different organisms- features that often have different functions but are structurally similar because of common ancestry

In multicellular organisms, only mutations in cells that produce gametes can

Be passed onto offspring and affect a population's genetic variabiliyu

Evolutionary tree

Biologists use this to represent patterns of descent

All life forms use the same genetic language of

DNA, RNA, and the genetic code

Evolutionary history of life where present day species arose from a succession of ancestors

Descent with modification

Homologous structures are both anatomical and molecular are used for

Determining the branch sequence of a tree

Sexual dimorphism

Distinction in appearance, size difference, forms of adornment (like a male lion's mane). Among vertebrates, males are usually the showier sex

Antibiotics

Drugs that kill infectious microorganisms. Naturally occurring chemicals derived from soil-Adwelling fungi or bacteria

Adaptions are often compromises

Each organisms must do many different things

Evolution is limited by historical constraints

Each species has a legacy of descent with modification by ancestral forms

Bottleneck Effect

Earthquakes, floods, or fires may kill large numbers of individuals, leaving a small surviving population that is unlikely to have the same genetic make-up as the original population. This drastic reduction in population size is known as the bottleneck effect

Molecular biology

Enables biologists to read a molecular history of evolution in the DNA sequences of organisms.

Hardy-Weinberg Principle

Equilibrium, where no matter how many times alleles are separated into different gametes and united in different combinations by fertilization, the frequency of each allele in the gene pool will remain constant unless other factors are operating

Stabilizing selection

Favors intermediate phenotypes and typically reduces variation and maintains the status quo for a particular character. I.e.: This type of selection keeps the majority of human birth weights in the range of 3-4 kg. Babies smaller or larger than this may have a greater infant mortality rate.

Sedimentary rocks

Form from layers of sand and mud that settle to the bottom of seas, lakes, and swamps

Founder effect

Genetic drift is also likely when a few individuals colonize an island or other new habitat producing a founder effect. The smaller the group, the less likely the genetic make-up of the colonists will represent the gene pool of the larger population they left.

Biogeography

Geographic distribution of species that first suggested to Darwin that organisms evolve from ancestral species

Population

Group of individuals of the same species that live in the same area and interbreed

Intersexual selection

Mate-choice. Where individuals of on sex (usually females) are choosy in selection of their mates.

In organisms that reproduce sexually,

Most of the genetic variation in a population results from the unique combination of alleles that each individual inherits

What did Charles Darwin realize that would cause an uproar about evolution?

Natural forces were gradually changing the Earth's surface and that these forces are still operating in modern times. Thus, the growth of mountains as a result of earthquakes could account for the presence of the marine snail fossils that he had collected on mountaintops in the Andes.

Selection can only act on existing variations

Natural selection favors only the fittest variants from the phenotypes that are available which may not be ideal traits.

What happens because of the sorting effect?

Only natural selection consistently leads to adaptive evolution- an evolution that results in a better fit between organisms and their environment

At some point in their development, all vertebrate embryos have a tail posterior to the anus as well as structures called

Pharyngeal (throat) pouches

Evolutionary fitness is related ti genes but it is an organism's _______( physical traits, metabolism, and behavior) that is directly exposed to the environment

Phenotype

Artificial selection

Process where humans have modified other species by selecting and breeding individuals with desired traits over many generations

The oldest known fossils are

Prokaryotes- dating back 3.5 billion years ago

The hereditary background of an organisms is documented in the DNA where ______are encoded there.

Proteins

Vestigial structures

Remnants of features that served important functions in the organism's ancestors.

Palentologists

Scientists who study fossils

Directional selection

Shifts the overall make-up of the population by acting against individuals at one of the phenotypic extremes. It is more likely to occur during periods of environmental chance or when members of a species migrate to some new habitat with different environmental conditions

Homology

Similarity in characteristics that results from common ancestry

What does comparative anatomy illustrate?

That evolution is a remodeling process in which ancestral species originally functioning in one capacity become modified as they take on new functions

Relative fitness

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

Evolution

The idea that Earth's many species are descendants of ancestral species that were different from those living today

Fossils

The imprints or remains of organisms that lived in the past

Fossil record

The sequence in which fossils appear within layers of sedimentary rocks which provides the strongest evidence of evolution

Gene pool

The total collection of genes in a population at any one time. Consists of all of the alleles in all individuals making up a population

Natural selection

The two inferences Darwin came up with about natural selection: 1. Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals 2. This unequal production of offspring will lead to the accumulation of favorable traits in a population over generations

Natural selection favored insects with alleles for pesticide resistance because

These insects left more offspring

Strata

When rocks form in layers Younger strata is on top

Microevolution

When the relative frequencies of alleles in a population change like this over a number of generations

Gene flow

Where a population may gain or lose alleles when fertile individuals move into or out of a population or when gametes are transferred between populations. It can reduce difference between populations. For example, humans today move more freely about the world than in the past, and gene flow has become an important agent of evolutionary change in previously isolated human populations

The frequencies of alleles will be mores stable from one generation to the next when

a population is large

Frequency- dependent selection

a type of balancing selection that maintains two different phenotypic forms in a population. IN this case, selection acts against either phenotypic form if it becomes too common in the population. An example of the F-D selection is a scale-eating fish in Africa that attacks other fish behind.

A gene that codes for a protein that breaks down an antibiotic or mutation that alters the site where

an antibiotic binds can make a bacterium and its offspring resistant to that antibiotic

Genetic Drift is when

chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next. The smaller the population, the more impact genetic drift is likely to have.

Most eukaryotes are

diploid. Having two sets of chromosomes helps prevent populations from becoming genetically uniform

Genetic drift, gene flow, and even mutation can cause micro-evolution but only by chance could these events result in ______

improving a population's fit to its environment

Heterozygote advantage

is a type of balancing selection in which heterozygous individuals have greater reproductive success than either type of homozygote with the result that two or more alleles for a gene are maintained in the population. An example of the heterozygote advantage is the protection from malaria conferred by the sickle-cell allele.

Disruptive Selection

is when environmental conditions vary in a way that favors individuals at both ends of a phenotypic range over individuals with intermediate phenotypes

The effects of recessive alleles may not often be displayed in diploid populations. A recessive allele is subject to

natural selection only when it influences the phenotype as only occurs in homozygous recessive individuals.

Balancing selection

occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population

Evolution by natural selection on the other hand is a blend of chance and

sorting: the chance in the random collection of genetic variation packaged in gametes and combined in offspring and sorting in that some alleles are favored over others in a given environment

Genetic drift as a result of a bottleneck reduced

the genetic variation of the population and may have increased the frequency of harmful alleles, leading to the low-hatching egg rate

Intrasexual selection

where in some species individuals compete directly with members of the same sex for mates. This type of sexual selection is within the same sex but most often males