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Flashcards in Evolution Deck (80):


Changes in populations, species or groups, changes in allele(traits) frequencies in populations over time.



Describes the details of how populations of organisms change from generation to generation and how new species originate.

Changes in allele frequencies that occur over time within a population(due to mutation, selection, gene flow & drift)



-also describe phylogeny

Patterns of changes in groups of related species over broad periods of geologic time. Patterns determine PHYLOGENY-evolutionary relationships among species and groups of species.)


Lamarack theory:

Use and disuse:

Describes how body parts can develop with increased usage, unused parts are weakened. - Common in athletes.


Lamarack theory:

Inheritance of acquired characteristics

Describes how body features can be acquired during lifetime (such as muscle bulk) - passed down to the offspring.


Lamarack theory:

Natural transformation of species

Describes how organisms produced offspring with changes, transforming each later generation slightly more complex


Darwin's Theory of Natural Selection:

Survival of the fittest(Darwinism). Also called neo-dawarnism.


Evidence for evolution

Paleontonlogy -

Provides fossils that reveal prehistoric existence of extinct species. Deepest fossils represent oldest specimens.


Evidence for evolution



Also state how it relates to continental drift.

Uses geography to describe distribution of species; unrelated species in different regions of the world look alike when found in similar environments.

Continental drift - how continuous slow movement of the plates


Evidence for evolution
Embryology: Describe

Closely related organisms that go through similar stages in their embryonic development.

ONTOGENY - Reveals similar stages in development among related species.

PHYLOGENY - The similarities help establish evolutionary relationship.
Ex- Gill slits and tails are found in fish, chicken, pig, and human embryos.


Evidence for evolution:

Comparative Anatomy

Describes two kinds of structures that contribute to the identification of evolutionary relationships. The two types: Homologous and Analogous structures.


Evidence for evolution:

Homologous Structures

Body parts that resemble one another in different species from common ancestor.

Ex- The wing of a bat, the lateral fin of a whale, and the human arm all have the same internal bone structure, although the function varies.


Evidence for evolution:

Analogous Structures

Body parts that resemble one another in different species because they evolved independently as adaptation to their environments.

Such as a bat's wing, and fly's wing, have the same function. However, the similarity is superficial and reflects an adaptation to similar environments, not descent from a recent common ancestor.


Evidence for evolution:

Molecular Biology

Examines nucleotide and amino acid sequences of DNA and proteins from different species. More than 98% of nucleotide sequences in humans and chimpanzees are identical.


Evidence for evolution:

Comparative Biochemistry

Organisms that have a common ancestor will have common biochemical pathways.
Ex- Humans and mice are both mammals.


Natural Selection:


Is the differences in survival and reproduction among individuals in a population as a result of their interaction with the environment.

-Responsible for producing ADAPTATIONS(superior inherited traits) that increase individual's FITNESS(ability to survive, leave offspring)


Natural Selection: 8 arguments for it

1. Populations posses an enormous reproductive potential:
2. Population size remain stable:
3. Resources are limited:
4. Individuals compete for survival:
5. There is a variation among individuals in a populationL
6. Much variation is heritable:
7. Only the most fit individuals survive
8. Evolution occurs as favorable traits accumulate in the population:

1. Populations posses an enormous reproductive potential: If all offspring produced and survived.

2. Population size remain stable:Populations fluctuate around a constant size.

3. Resources are limited: Resources do not increase as population grow larger.

4. Individuals compete for survival: Growing pop will exceed available resources

5. There is a variation among individuals in a population: Such as skin color(very pale to very dark)

6. Much variation is heritable:DNA passed down.

7. Only the most fit individuals survive : survival of the fittest

8. Evolution occurs as favorable traits accumulate in the population: Best adapted individuals => best adapted offspring leave most offspring.


Natural Selection: Stabilizing selection

Sometimes called purifying selection, eliminates the extremes and favors the more common intermediate forms.

Ex- In humans, stabilizing selection keeps the majority of birth weights in the 6-8 pound range.


Natural Selection: Directional selection:

Has two examples; Peppered moths and Insecticide resistance

Favors traits that are at one extreme of a range of traits.

(Industrial melanism)Peppered Moths - Selection of moth color from a light to a dark color. Before the industrial revolution, the light from of the moth was well camouflaged. After the industrial revolution, the dark moth never was able to to be observed , and therefore, increased in frequency.


Natural Selection: Sexual Selection


What is Sexual Dimorphism

A selection based on variation in secondary sexual characteristics related to competing for and attracting mates. In males, the evolution of horns, antlers, large stature, and great strength are the result of sexual selection.

Female choice: leads to traits/behaviors in male that are favorable to female, favors traits like colorful plumage. Results in sexual dimporphism.

Sexual Dimorphism: Differences in appearance of males and females => becomes a form of disruptive selection.


Natural Selection: Artificial Selection

Form of directional selection carried out by humans when they breed favorable traits

Ex- Humans breeding various breeds of dogs like Dobermen


Sources of Variations:


Introduces a new allele.


Sources of Variations:

Sexual Reproduction -

Provides variation due to the shuffling and recombination of alleles during meiosis and fertilization. Creates a new combination of alleles.

These rearrangements or GENETIC RECOMBINATION, originate from 3 events during sexual reproductive process: Crossing Over, Independent assortment of homologues, Random joining of gametes.


Three events of Sexual Reproduction:

Crossing Over
Independent assortment of homologues
Random joining of gametes

Crossing Over - Exchanges of DNA between sister chromatids of homologous chromosomes, occurs during prophase I of meiosis

Independent assortment of homologues - during metaphase I creates daughter cells w/ random combinations of maternal and paternal chromosomes.

Random joining of gametes - during fertilization contributes to the diversity in the zygote.


Sources of Variations:


Presence of two copies of each chromosome.

In the heterozygous conditions, recessive allele is stored for later generations => more variations is maintained in gene pool.


Sources of Variations:


Mating with unrelated partners => mixing different alleles => new allele combinations


Sources of Variations:

Balanced polymorphism

The presence of two of more phenotypically distinct forms of a trait in a single population of a species.

Examples of polymorphism(the coexistence of two or more different phenotypes) are observed in many populations.

Ex- A good example is sickle-cell anaemia:
A person who inherits the sickle cell gene from one parent, and a normal hemoglobin gene from the other, has a normal life expectancy, but is a carrier of sickle cell trait, and is resistant to malarial parasites.


Sources of Variations:

Balanced Polymorphism --- Heterozygote advantage

Heterozygote= having mismatched alleles of a gene. It is a phenomenon in which the hybrid individual is selected for because it has greater reproductive success. The hybrids are sometimes better adapted than the homozygotes.

But if there is a heterozygote advantage, then carriers of the disease (people who are heterozygous, with one normal allele and one for the disease) will be more likely to survive than people without the disease allele. Since the allele helps survival, it will spread throughout the population. This seems to be why some genetic diseases are very common.


Sources of Variations:
Balanced Polymorphism --- Hybrid vigor(heterosis)

Describes the superior quality of offspring resulting from crosses between two different inbred strains of plants.

Ex- A hybrid of corn, developed by crossing two different corn strains that were highly inbred, is more resistant to disease and produces larger corn ears that either of the inbred strains.


Source of Variations:

Frequency-dependent selection(minority advantage)

Least common phenotypes have a selective advantage. This acts to decrease the frequency of the more common phenotypes and increase the frequency of the less common ones.

Ex- In predator-prey relationships, predators develop a "search engine" that enables them to hunt a particular kind of prey effectively. The prey that is over, escaped predation.


Sources of Variations:

Neutral Variation-

Variation w/out selective value (e.g. fingerprints in humans)


Sources of Variations:

Geographic Variation- Describe
-Cline/North-south cline

Variation of a species dependent on climate or geographic conditions. A graded variation of a phenotype due to this is known as a CLINE; Variation from north/south environments is a NORTH-SOUTH CLINE.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population


Increase/decrease of allele frequencies due to environment.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population


Describes the introduction or removal of alleles from the population when individuals leave(emigration) or enter (immigration) the population.
EX- pollen from one valley can be carried by the wind across a mountain to another valley.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population


A random increase or decrease of alleles. In other words. some alleles may increase or decrease for no other reason than by chance.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population

GENETIC DRIFT: Founder Effect

Allele frequencies in group of migrating individuals are (by chance) not the same as that of their population origin.
Ex- a small group of Germans began a Amish community that possessed an allele for polydactylism(extra fingers/toes)


Causes of Changes in Allele Frequencies/ Causes of evolution of a population


Occurs when population undergoes a dramatic decrease in size(natural catastrophe, volcano) has created many populations of plants and animals.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population

Nonrandom mating:

Individuals choose their mates for a specific reason.
Ex- Blue snow geese tend to mate with blue geese, and white geese tend to mate w white geese.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population


Individuals mate w relatives.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population


Females choose males based on superior traits.


Causes of Changes in Allele Frequencies/ Causes of evolution of a population


Changes in genetic material. A single point mutation can introduce a new allele into a population.


Genetic Equilibrium( Hard-Weinberg Equilibrium)

Say 5 conditions

Allele frequencies remain constant from generation to generation.

1.All traits are selectively neutral( no natural selection)
2. Mutations do not occur.
3. The population must be isolated from other populations (no gene flow)
4. The population is large (no genetic drift)
5. Mating is random.


Genetic Equilibrium is determining by evaluating the following values: 3 values

1. Allele frequencies for each allele (p,q)
2. Frequency of homozygotes (p^2,q^2)
3. Frequency of heterozygotes (pq + qp = 2pq)


Genetic Equilibrium: 2 equations

1.p+ q = 1 (all alleles sum to 100%)
2. p^2 + 2pq + q^2 = 1 (all individuals sum to 100%)


Genetic Equilibrium: Read and understand an example

Suppose a plant population consists of 84% plants w red flowers and 16% with white flowers. Assume the red allele (R) is dominant and the white allele (r) is recessive.

q^2 = 0.16 = white flowered plants (rr trait)
p^2 + 2pq = 0.84 = red flowered plants (RR and Rr trait)

To determine the allele frequency of the white flower allele, calculate q finding the square root of q^2.
q = square root 0.16 = 0.4

Since p +q = 1. P must equal 0.6.

You can also determine the frequency or individuals with homozygous dominant and heterozygous

2pq = (2)(0.6)(.4) = 0.48 or 48% = heterozygotes
p^2 = (0.6)(0.6) = 0.36 or 36% = homozygotes dominant.



Formation of new species.



A group of individuals capable of interbreeding.


Allopatric Speciation:

Is caused by geographic isolation separation by mountain ranges, canyons, rivers, lakes, glaciers, altitude.

Interbreeding between the populations will not occur if the barrier is removed.


Sympatric Speciation:

Formation of new species without presence of geographic barrier.
Sympatric speciation is rare. It occurs more often among plants than animals, since it is so much easier for plants to self-fertilize than it is for animals.


Sympatric Speciation: Balanced Polymorphism

Natural selection due to polymorphism.

Example: different color in insects, one color can camouflage to different substrate, and the other that cant will be eaten. Only insects with same color can mate( isolated from other subpopulations)


Sympatric Speciation: POLYPLOIDY

Organisms that contain two sets of chromosomes found in diploid (2n) cells. Polyploidy often occurs in plants (and occasionally animals)

(3n, 4n in plants two viable diploid gametes and two sterile gametes w no chromosomes => tetraploid 4n zygote formed => repeat w diploid gametes male/female => reproductive isolation w normal gametes.


Sympatric Speciation: HYBRIDIZATION

a hybrid is mix of two animals or plants of different breeds, varieties, species or genera

The act or process of mating organisms of different varieties or species to create a hybrid.

HYBRID ZONE-A region where two related populations that diverged after becoming geographically isolated make secondary contact and interbreed where their geographical ranges overlap.

(more genetic variations => hybrid can live beyond range of either parents.)


Sympatric Speciation: ADAPTIVE RADIATION

The relatively rapid evolution of many species from a single ancestor; occurs when ancestral species is introduced to an area where diverse geographic/ecological conditions are available for colonization.


Maintaining Reproductive Isolation:

Prevent gene flow(no separation by geo barrier; may be random or result of NS)


Maintaining Reproductive Isolation:

Prezygotic Isolating mechanism-

Prevents fertilization.


Maintaining Reproductive Isolation:


Species do not encounter.


Maintaining Reproductive Isolation:


Occurs when a species does not recognize another species as a mating partner because it does NOT perform the correct courtship rituals.


Maintaining Reproductive Isolation:


Male/female genitlia are NOT compatible


Maintaining Reproductive Isolation:


Male gametes do not survive in environment of female gametes( gametes do not recognize others)


Maintaining Reproductive Isolation:


Prevent fertilization.


Maintaining Reproductive Isolation:


Zygote fails to develop properly and dies before reaching reproductive maturity.


Maintaining Reproductive Isolation:


Hybrids become functional adults but cannot reproduce.


Maintaining Reproductive Isolation:


Hybrids produce offspring that have reduced viability or fertility, (hybrid's children cant reproduce!)


Patterns of Evolution:

Divergent Evolution-

Describes Two/more species that originate from common ancestor and become increasingly different over time(result of speciation).
Ex- A birds having different shapes and sizes of beaks.


Patterns of Evolution:

Convergent evolution:

Describes two unrelated species that share similar traits by environment( analogous traits)

Ex - sharks, penguins have torpedo shaped bodies. These traits arise as a result of adaptations to aquatic life and not because these animals inherited these traits.


Patterns of Evolution:

Parallel Evolution-

Describes two related species that have made similar evolutionary changes after their divergence from a common ancestor.

Ex- marsupial mammals of Australia and the placental mammals of North America. Grey wolf of North America and marsupial Tasmanian wolf of Australia.


Patterns of Evolution:


Evolution of one species in response to new adaptations that appear in another species (predator/prey)
- The butterfly exhibits bright conspicuous warming colors that deter predators.



Describes patterns of evolution for groups of species over extended periods of geologic time.


Phyletic Gradualism:

Evolution occurs by gradual accumulation of small changes; but unlikely to be valid because intermediate stages of evolution are missing(no fossils); fossils only reveals major changes in groups of organisms.


Punctuated Equilibrium

Evolutionary history consists of geologically long periods of stasis (stability) w little/no evolution followed by geologically short periods of rapid evolutions. Absence of fossils revealing intermediate stages of evolution is considered data that confirms rapid evolutionary events.


Origin of Life-

Primordial Seas Formation:

As earth cooled ==> gases condensed ==> sea with water and minerals.


Origin of Life-

Polymers and self-replication:describe

-also, what is Proteinoids

Monomers => Polymers (dehydration concentration)

Proteinoid's are abiotically produced polypeptides. They can be experimentally produced by allowing amino acids to dehydrate on hot, dry substances.


Origin of Life-

Organic molecules were concentrated/isolated into protobionts.

Aggregate- formed by the conjunction or collection of particulars into a whole mass or sum; total; combined

Precursor - : something that comes before something else and that often leads to or influences its development.

Protobionts- they are the precursors of cells. They were able to carry out chemical reactions enclosed within a border across which materials can be exchanged, but were unable to reproduce.


Origin of Life-

Microspheres/liposomes and coacervates.

They are experimentally (and abiotically) produced protobionts that have some selectively permeable qualities.


Origin of Life-

Primitive heterotrophic prokaryotes -


-Obtained materials by consuming other organic substances (pathogenic bacteria)

Heterotrophs - living organisms that obtain energy by consuming organic substances.


Origin of Life-

Primitive Autotrophic prokaryotes

As a result of mutation, a heterotroph gained ability to produce its own food.

Cyanobacteria - autotrophic prokaryotes that obtain energy and manufacture organic compounds w photosynthesis.


How Eukaryotes were formed: Edosymbiotic Theory


Eukaryote cells orginated mutually among prokaryotes (mitochondria, chloroplast establish resident inside another prokarytoes.

EVIDENCE: Thylakoid membranes of chloroplasts resemble photosynthetic membranes of cyanobacteria, mitochondria and chloroplasts have their own circ. DNA , they reproduce independently.


Which of the following generates the formation of adaptations?

A) Genetic Drift
B) Mutations
C)Gene Flow
D)Sexual Reproduction
E) Natural Selection

E) Only natural selection generates adaptations. Changes in gene frequencies from other factors may contribute to increases fitness but not because they produce adaptations.

For example, mutations may introduce a new allele, but the allele will lead to an adaptation only if it increases in the population as a result of natural selection.


The B blood-type allele probably originated in Asia and subsequently spread to Europe and other regions of the world. This is an example of.....

Gene flow. It is the increase in allele frequencies due to transfer from other populations.


The appearance of a new mutation is....

A random event. Mutations occur randomly and are usually harmful. Whether or not the mutation increases or decreases in frequency in the population is the result of natural selection, genetic drift, gene flow, or nonrandom mating.