BIS 002B Final Exam Terms

Catastrophism

Earth and life on it are primarily shaped by major, sudden events

Gradualism

Earth and life on it are primarily shaped by long, slow processes '

Descent with modification

species share a common ancestor and have diverged gradually through time

ex. same limb bones in all tetrapods, adapted to different purposes

Natural selection

changes in species through time are due to increased survival and reproduction of some individuals over others, based on differences in their traits

Homologous traits

produced by descent with modification; they are similar in different organisms because they are inherited from the common ancestor

Analogous traits

produced by convergent evolution; they are similar in different organisms because of similar selective pressure

Ex. fins in sharks and dolphins

Vestigial structures

A structure/trait that wasted away or no longer “serves an obvious purpose”
- these traits used to be useful for ancestors, but we don’t really know why they disappeared

Evolution

changes in the frequencies of a trait in a population over generations

Development

changes within an individual during a lifetime (acclimation)

Microevolution

small-scale changes in allele frequencies across generations

Macroevolution

large-scale changes and long time frames (geologic time scales)

Stabilizing selection

phenotypes nearest the mean have the highest fitness —> mean stays the same and variation is reduced

Directional selection

phenotypes at one extreme have the highest fitness —> mean trends toward that extreme overtime

Disruptive (diversifying) selection

phenotypes at both extremes have higher fitness than the mean —> variation is increased and bimodal pattern emerges

Frequency-dependent selection

Rarer phenotype has the highest fitness —> frequency of a given phenotype oscillates (swings back and forth)

Sexual selection

natural selection on traits that affect the likelihood of obtaining a mate

Intrasexual selection

within the same sex (territory, status)

Intersexual selection

one sex is ‘choosy’ —> mate choice

Altruism

a behavior that reduces individual fitness and increases the fitness of other individuals (help others reproduce and delay their own reproduction)

Kin selection

favors behaviors that increase the reproductive success of relatives (helping relatives is just as good as helping yourself)

Inclusive fitness

the sum of an individual’s own fitness, and its contribution to the success/survival of relatives

Law of Segregation

when any individual produces gametes, the two copies of a gene separate so that each gamete receives only one copy

Law of Independent Assortment

alleles of different genes assort independently of one another during gamete formation

Complete dominance

a single dominant allele produces the dominant phenotype, so the homozygous dominant and heterozygous genotypes have the same phenotype

Incomplete dominance

heterozygote phenotype is intermediate between the two homozygous phenotypes (ex. red and white flower creates pink flower)

Codominance

the heterozygote shows both of the homozygous phenotypes (ex. speckled chickens with black and white feathers)

Genotype

an individual’s particular alleles at a gene/locus

Phenotype

an individual’s observable trait

Homozygous

two identical alleles

Heterozygous

two different alleles

Pleiotropy

when one gene affects multiple traits

Polygenic inheritance

one trait/phenotype is controlled by many genes

Epistasis

when multiple genes interact in a non-additive way to determine the phenotype (in other words, the expression of one gene is suppressed/masked by the expression of one or more genes)

Extension gene

recessive trait that lacks any pigment (ex. dog fur)

Allopatric populations

populations of different species/types that do not overlap geographically

Sympatric populations

populations of different species/types that are partially or completing overlapping (geographically)

Allele frequencies

the proportion of a particular allele across all individuals, or in the gametes produced by those individuals

Genotype frequencies

the proportion of individuals with a particular genotype in a population

Hardy-Weinberg Equilibrium

as allele frequencies remain the same and mating is random, genotype frequencies will remain the same across generations
- No mutations
- No natural selection
- No gene flow (no migration)
- No genetic drift (requires a large population size)
- random mating

Gene flow

includes movement of individuals or gametes
- may introduce new alleles into a population and lead to an excess of homozygotes

Genetic drift

Chance events that cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations

The Founder Effect

a new population is created with few individuals from the initial population

Genetic Bottlenecks

when population size is severely reduced due to biotic/abiotic factors (similar to a founder effect, but all within a single population)
- diversity is slow to recover since it requires new mutations or gene flow from other populations

Positive assortative mating

mating preferentially happens between individuals with similar genotypes (inbreeding)

Outbreeding/negative assortative mating

mating preferentially happens between unrelated individuals with dissimilar genotypes

Hybrid offspring

result of interbreeding between individuals of 2 different species

Biological Species Concept

A species is a group of actually or potentially interbreeding natural populations that are reproductively isolated from other groups

Lineage Species Concept

A species is a group of organisms that shares a common ancestor and can be distinguished from other organisms by particular traits

Morphological Species Concept

A species is a group of organisms that have similar physical traits

Reproductive isolation

• fundamental driver of speciation

• the prevention of viable and fertile offspring from being created between two populations (prevention of gene flow)

Prezygotic barriers

prevent mating/fertilization if mating occurs

Postzygotic barriers

prevent a hybrid zygote from developing into a viable, fertile adult

Habitat isolation

species occupy different habitats, never come into contact

Temporal isolation

breed during different times

Behavioral isolation

individuals do not recognize each other as potential mates

Mechanical isolation

physical differences between the organisms prevent successful mating

Gametic isolation

sperm is not able to fertilize the egg

Reduced Hybrid Viability

F1 hybrid offspring do not complete development or have low survivorship

Reduced Hybrid Fertility

F1 hybrid offspring are viable, but have reduced fertility/fecundity

Hybrid Breakdown

F1 hybrid offspring are viable and fertile, but offspring of these hybrids (F2) are inviable or sterile

Phylogenetic Trees

A graphical depiction of the history of relationships among a group of organisms
- the shorter the distance back to most recent common ancestor, the more closely related

Polyploidy

Having more than 2 sets of chromosomes

Allopolyploidy

The polyploid carries the combined genomes of two separate species

Autopolyploidy

The polyploid carries the duplicated genome of a single species

Symbiosis

an interaction between two species living in close association with each other (does not necessarily have to be a positive interaction)

Amensalism

a type of biological interaction where one species causes harm to another organism without any cost or benefits to itself

Commensalism

an association between two organisms in which one benefits and the other derives neither benefit nor harm.

Mutualism

a relationship between two organisms in which each of the organisms benefits (obligate for a species if that species cannot survive without the presence of another species)

Crypsis

blending into environment to reduce chance of detection

Mimicry

species looking similar
(Ex. mullerian mimics are a group of species that are well-defended and look similar to each other —> predators will avoid them)

Keystone species

a species that plays a large role in the stability and overall diversity of a community

Adaptive Radiation

• an evolutionary radiation occurs when rapid speciation results in a burst of new species from one ancestor

• definition of term: it occurs when this radiation results in species adapted certain environments and filling different ecological niches

Fundamental Niche

The abiotic conditions in which a species can survive and reproduce (temperature, precipitation, soil type) It represents the full range of conditions and resources a species can utilize in the absence of competitors.

Realized Niche

The real conditions in which a species occurs in the wild—it incorporates biotic conditions (interactions with other species) as well as abiotic conditions

Intraspecific competition

competition for resources among members of the same species

Interspecific competition

competition for resources between members of different species

Competitive exclusion principle

states that two species cannot coexist if they occupy the same niche (competing for identical resources) This principle implies that one species will outcompete the other, leading to the local extinction of the less competitive species.

Resource Partitioning

species coexist by using resources in different ways (ex. different locations in the habitat or different parts of the resource)

Character displacement

Species competing for the same resource may diverge in “morphology” due to natural selection (differences in physical traits help reduce competition such as varying beak length)

Conditional Interactions

Interactions between species that vary depending on environmental conditions or the presence of other species, influencing the nature of competition, predation, or mutualism.

Succession

the change in species composition within a community over time

Primary succession

refers to change where nearly all life is removed (often there is no soil)

Secondary succession

refers to change where most of a biotic community is lost, but not all

Tropical Rainforest

• High precipitation and temperature

• Low seasonality (variation) in both precipitation and temperature

Desert

• Low precipitation

• very high, seasonal temperature

• Precipitation is rare and unpredictable

“Pulse-reserve” paradigm

• rainfall in desert triggers a burst of plant growth/reproduction (will be stored as seeds in the soil)

• many vertebrates are granivores (seed-eaters) and will take advantage of these seeds stored in the soil

Temperate Grassland

• Fairly low precipitation

• Seasonality (variation) in temperature and precipitation

• Always have dry/cold seasons with low precipitation

Mediterranean

• Very vulnerable to fire

• Seasonality in temperature and precipitation

• The hottest months are driest months (different from grasslands —> when it is hot, it is wet in grasslands)

Temperate Deciduous Forest

• similar to grasslands, but more precipitation —> wetter —> more trees

• seasonality in temperature (for tropical rainforests, there is barely any seasonality)

• No dry seasons

• 0-3 months of freezing

Boreal Forest

• Seasonal cold temperatures (5-8 months of freezing temperatures)

• Moderate precipitation, no real dry season

• Colder version of temperate forest

Tundra

• “desert of the north”

• AT LEAST 9 months below freezing temperatures

• frozen water in soil (permafrost) —> barely any root growth —> less trees

Grasslands

• graph shows that at higher precipitation, it is hotter

• key idea: when it is hot, it is wet

Massive algae bloom

• Is a result from nutrient pollution (too much nitrogen and phosphorus in the area)

• however, when these nutrients run out, the algae will die —> there will be less oxygen getting produced

• Decomposers will break down on these dead algae, taking away all the oxygen and producing more CO2, which is BAD >:(

Net primary productivity (NPP)

• how much carbon on net is taken up by plants/primary producers

• GPP - rate of respiration

Gross Primary Productivity

rate of photosynthesis

Lindeman’s Law of 10%

On average, roughly 10% of energy available at one trophic level is transferred to the next trophic level

Ecological efficiency

proportion of net primary energy that becomes new secondary energy (consumption x assimilation x production efficiencies)

Foundation species

a species whose presence has a significant impact on the rest of the community because of its high abundance or large size and its creation of food/habitat

Ecosystem engineer

a species that creates, modifies, or maintains physical habitat for themselves and other species

Top down effects

Change in predator abundance (top trophic level) can impact whole food web