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47 Cards in this Set

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Charls Lyell disagreed 1797- 1875

He disagreed with the then-popular theory called catastrophism, which dictated thatenvironmental changes were caused by catastrophes and occurred abruptly, entirespecies dying out and being immediately replaced by others

Charls Lyell agreed

agreed instead with the previous ideas of a geologist named James Hutton, whobelieved that the Earth must be very old and that geological and environmental changesmust occur very gradually over long periods of time and conform to natural scientificlaws. This theory became known as uniformitarianism


He believed that the number of offspring born in a population would outnumber thatwhich could sustainably survive

Charles Darwin was very influenced by

Lyell and Malthus. He usedelements from both of their theories to reinforce the theory of gradualism – the belief thatevolutionary change occurs in slow, gradual stages

Stephen Jay Gould

the theory of punctuated equilibrium, which hedeveloped with Niles Eldredge and proposed in 1972



Niles Eldredge

He is a currently active biologist and paleontologist specializing in the evolution of trilobites, which are a type of extinct arthropod

He co-authored the theory of punctuated equilibrium with Thomas Gould in 1972,concluding that evolution does not only happen gradually over time, but can also occur inconcentrated bursts

Allele Frequency:

How often a gene variant (allele) occurs in a population.


is the only change in DNA that creates anew random allele, and is the only way a new alleleor additional genetic information can be added.can also be causedby chemicals and radiation that break down DNA. Ifthe affected cell tries to repair the DNA and makesmistakes, mutations occur

Mutation changes...

allele frequency and createsgreater variation and diversity in a species’population. It is also the original source of variation

Genetic Drift:

drift is the change in allele frequency in a population due to chance alone, ratherthan natural selection● It generally only occurs in small populations


Reduces genetic diversity, which can reduce the population’s ability to evolveo Negatively impacts rare and endangered species, because genetic drift has moredrastic effects on small populationso Contributes to speciation; the emergence of new species

Gene Flow (Migration):

The “net movement” / flow of alleles

When individuals who are fertile migrate, they change the allele frequencies of both the population they enter, and the population they leave. This is also for when individuals from neighbouring populations mate

Population Bottlenecks/The Bottleneck Effect:

The bottleneck effect is when the size of a population rapidly decreases, causing achange in the gene pool

The Founder Effect:

The founder effect occurs when afew individuals (founders) from alarge, original population establish anew colony, creating a change inthe gene pool

Directional selection

deals with the favouring of 1extreme phenotype over the general phenotype. Thiswould cause the general phenotypic trait to movetowards the favourable conditions of theenvironment, which will then result in an increase inadaptation.

A classic example of directional selection would bethe evolution of the peppered moths.

Stabilizing Selection

refers to a type of selection in which an intermediate trait is chosen over two possible extreme phenotypes for survival. It maintains the mean value for the trait, and subsequently decreases variation for the trait (resulting in a decreased genetic variation) An example of this can be found in human birth weights.

Disruptive selection

occurs when species’ traits vastly different from each other are favored during natural selection. These are incomplete dominant traits that cause disruptive selection. These opposite traits are wedged apart due to several factors that eliminate any species in the middle of these traits.

Principles of Sexual Selection:

Traits within an organism that can aid in their mating success• Organisms with advanced traits are more likely to pass on traits tonext generation

Inter-Sexual Selection (sexual dimorphism):

The differences in physical appearance of males and females• Females in some species choose mates bases on physical appearancesor through song

Intra-Sexual Selection (male-male competition):

This is usually responsible for male armaments which give themadvantages in fighting


Altruism is when one organismʼs behavior benefits another organism, at a cost to itself

This means an increase in the fitness of the organism being aided, and a decrease in the fitness of the individual that is assisting or cooperating with the recipient individual.

Kin Selection:

It is based on the concept of inclusive genetic fitness, which suggests that altruismamong organisms that are related / genetically similar, enhances the genetic fitness ofboth the recipient of the act and the altruistic organism.

Hamiltonʼs rule equation:

His rule mathematically describes weather or not the altruistic gene will spread amongst a population. “r” stands for the degree of relatedness “c” stands for the cost of the altruists “b” stands for the number that measures the benefit the acceptor gained from the altruistic activity.


Reciprocal Altruism:

“Iʼll scratch your back if youʼll scratch mine.”


The formation of new species due to physical, anatomical, geographical and/or behavioral factors

Allopatric speciation

is the formation of new species because of geographicalbarriers. When organisms of the same species are separated physically, they canevolve separately and form new gene pools, creating new species.

Sympatric speciation

is the formation of new species due to reproductive barriers.


If two of the original species are no longer able tointerbreed, they will then be classified as new species.

Pre-zygotic Isolating Mechanisms:

Behavioral Isolating System - Two species with ecosystems that overlap but are differentiated by behavior. Example: The eastern meadowlark's song is a simple whistle of few notes while the western meadowlark's song is longer and flute-like.  Habitat Isolating System - Two species that live within the same region but are separated by habitat. Example: The northwest garter snake prefers meadows and rarely enters water while the common garter snake is commonly found near water.  Temporal Isolating System - Two species that live in the same area but are separated by timing barriers. Example: Three species of tropical orchid in the Dendrobium genus only bloom for a single day: opening at dawn and withering at dusk.  Mechanical Isolating System -Two species that could be closely related but cannot achieve fertilization due to anatomical differences. Example: flowers, which attach pollen to bee's wings and flowers, which attach pollen to bee's backs. Speciation  Gametic Isolating System -Two species gametes meet but do not likely form a fertile zygote. Example: sperm not being able to survive in the reproductive track of a female.

Post-zygotic Isolating Mechanisms

Hybrid Inviability - Interbred species may stop development of the fertile zygote. Example: sheep/goat hybrid die in early development.  Hybrid Sterility -Interbred species are born successfully but is born sterile. Example: donkey/horse can reproduce to make a mule but mule cannot mate with other mule successfully.  Hybrid Breakdown - Interbred species is born successfully and can reproduce with other hybrids but the offspring of two hybrids are weak and die. Example: two species of cotton breed to make fertile hybrids but offspring of hybrids die in early development.

Divergent Evolution:

Divergent evolution is when species from one common ancestor evolveincreasingly different due to varying environments, or selective forces. Theancestor species can evolve into diverging species that become more and moredifferent. Divergent evolution can occur very rapidly, or at the same time amongmany populations. Their traits are homologous.

Convergent Evolution:

Convergent evolution is when two or more species become increasingly similarbecause of similar selective and environmental pressures INDEPENDENTLY.The traits that are similar in appearance, but different in evolutionary ancestorsare known as homoplasies (i.e. analogous features).Species closely related, develop the same traits as a result of similarenvironments and/or niches.

How are Fossils formed?

When these hard materials are covered in layers of sediment, they are compressed and replaced by minerals (calcite, pyrites, silica, etc.) crystallizing out of water by a process called mineralization

Pentadactyl Limb-

The pentadactyl limb has 5 digits on the end of each limb. It also has a specific pattern of bones. It is common in mammals, birds, reptiles, amphibians and dinosaurs. It is also common in most four limbed creatures, which shows humans’ ancestry with amphibians, mammals and reptiles. Examples of homologous pentadactyl limbs are: Human hands and feet, bat wings, and whale and dolphin fins. Ancient animals that were alive 380-360 million years ago had varying digits. Some had up to 8 digits before 5 became common.

Stingers and the Ovipositor-

Female bees, wasps and hornets have stingers, which they use to inject poison. These stingers are modified versions of egg laying devices called ovipositors, which are attached to poison glands. In the case of insects with stingers, the eggs emerge from the base of the ovipositor instead of going through it. The stinger and the ovipositor are structurally similar yet they serve different purposes and are therefore homologous features.


Analogous features are two or more morphological features of different animals thatare structurally different but serve the same purpose.

convergent evolution.

when two species evolve the same traitsindependently of one another, due to similar environmental pressures.


The insect wing ismade up of membranes, however, both the bird wing and the insect wing serve thepurpose of flight. Because they are structurally different but serve the samepurpose, these two different types of wings are analogous to each other.

Shark Fins and Dolphin Flippers-

Sharks and dolphins evolved separately, yetthey both live in salt-water oceans and both possess structures used for swimming.Once fish evolved to become land mammals, some mammals moved back into theocean like whales and dolphins. This proves that sharks and dolphins evolvedseparately yet developed the same traits (swimming structures) due to selectivepressures from the same aquatic environment.


Vestigial features are morphological features present on an animal that serve no purpose, or are far too complicated for the purpose that they serve.

Wings on flightless birds-

birds. Flightless birds retain many of the other aspects of their airborne cousins like beaks and feathers but the wings are used for less complex tasks like stabilization while running.

Pelvic bones of whales-

The pelvic bone on a whale is essentially useless and the fact that these water mammals have bones that would normally be found on land mammals supports the theory that whales evolved after early land mammals when they “crawled” back into the ocean.

Bergmann’s Rule:

The rule says that birds and mammal species that live in a colder climate are bigger than the same species in a warmer habitat. Bergmann realized that big animals are more advantageous than smaller ones in cold climates because it makes it easier for the animal to stay home. Whereas animals with lower body surface area in warm climates are more advantageous because more heat loss can occur.

Gloger’s Rule:

The rule states that species of birds andmammals that are in warmer and/or humid regions aremore darkly coloured than species of colder or drierregions. The explanation for this is that animals that arein warmer climates need more pigmentation to protecttheir cells from the sun’s UV radiation

Allen’s Rule:

Endothermic animalsthat reside in colder regions tend tohave smaller body parts than thosewho live in warmer regions. Thisincludes the tail, ears and legs etc.This reduces their surface; volumeratio.

Adaptive Radiation

When one single ancestor of a species diverges throughspeciation to occupy and use a vacant adaptive habitat/area.

Island Biogeography

The number of species found on an undisturbed island is determined by immigration and extinction. Immigration and emigration depends on the Distance effect, which is the distance of an island from a source of colonists. The extinction rate of a colonized island is affected by the size of the island (area affect) For example a larger island means that there will be more varities of animals because of its different habitats. This reduces the chance of extinction.