Bio 305 - Exam 1

ecology

Study of interactions between organisms and their environment, and how those interactions affect the distribution and relative abundance of organisms 

“ontogeny recapitulates phylogeny”

Ernst Haeckel (1800’s) argued embryos go through their evolutionary tree before achieving final form

Johannes Eugenius Warming (1800’s)

First person to publish ecology textbook

Arthur Tansley

Student of Warming, coined term ecosystem

Stephen Forbes (1800’s)

Made first significant publication in ecology, promoted natural recreation areas, from Illinois

Ellen Swallow Richards

First women in PhD program at MIT, advocate for using ecology to improve conditions, used chemistry for nutrition

G. Evelyn Hutchinson

Transformed ecology into an analytical science

Robert H. MacArthur (1900’s)

Student of Hutchinson, R and K selection

Charles Darwin (1800’s)

The Origin of Species

Alfred Russel Wallace (1800’s)

Geographical Distribution of Animals - collected specimens and sold them to European collectors

Jean Baptiste Lamarck (1700’s)

Theory of Acquired Characteristics through studying giraffes

Patrick Matthew (1700’s)

Wrote natural timber, described evolution via natural selection, fruit farmer and forester

G. Evelyn Hutchinson (1900’s)

Provided the most recent definition of species niche as “n-dimensional hypervolumes”

Proximate explanations

Mechanistic and explain how

Ultimate explanations

Evolutionary and explain why

Entry rules

Biases in nature that determines who joins the group

Exit rules

Biases in nature that determines who leaves the group

Transformations

Changes caused by processes that act upon individuals

Why are hot peppers hot?

Hot peppers contain capsaicin

Baker’s Law

Angiosperms on islands are more likely to be self-compatible than those on the mainland

Biological evolution

Decent with modification, or changes in allele frequency over time

Natural selection

Nonrandom process where biological traits sway based on the survival and reproductive output of those that have them

Genetic drift

Any allele frequency changes due to random events. Caused by founder and bottleneck effect

Mutations

Includes small-scale changes such as single-nucleotide point mutations, large-scale whole-genome duplications (polyploidy), and changes on the immediate scale (inversions, deletions)

Gene flow

Movement of genetic material (alleles) from one population to another. Homogenizes gene pools

Nonrandom mating

The process where individuals are engaging in sexual selection

What conditions are needed for evolution via natural selection to occur?

1. The trait must exhibit variation 

2. Variation of the train must be correlated to survival and reproductive output 

3. At least some variation must be heritable 

Directional Selection

Selection for phenotypes at one end of a phenotypic distribution (mean changes, variation decreases)

Stabilizing Selection

Selection for phenotypes at the middle of phenotypic distribution (mean stays the same, variation decreases)

Disruptive Selection

Selection for phenotypes at both ends of a phenotypic distribution (mean stays the same, variation increases)

Founder effect

Occurs when a new population is founded by a group of individuals that migrated from somewhere else (imagine accidentally introducing a species to a new country)

Bottleneck effect

Occurs when a population experiences a large and rapid reduction in size (often a huge event like a forest fire)

Why did I argue that biases in the production and union of gametes cause genetic drift?

Not all organisms choose to reproduce, and not all organisms have an infinite number of gametes. This leads to sampling error and random changes in allele frequency over time.

Effective population size

Considers the fact that not all organisms reproduce and that a catastrophic event could happen

Positive assortive mating

Organisms are more likely to mate with organisms that are like themselves 

Negative assortive mating

Organisms are more likely to mate with organisms different from themselves 

Ex. MHC in humans through pheromones 

Inbreeding depression

A reduction in the fitness of inbred individuals compared to non-inbred individuals

Partial dominance model

Inbreeding depression is caused by recessive deleterious alleles that are exposed int he homozygotes

Overdominance model

Inbreeding depression is due to decreased heterozygosity 

Population

A group of conspecifics in the same place at the same time

Fundamental niche

The physical/abiotic conditions under which a species might live in the absence of interactions with other species 

Realized niche

The actual niche of a species whose distribution is influenced by biotic interactions such as competition, predation, etc.

Joseph Connell

Represented fundamental vs realized niches through barnacle competition

Competitive exclusion principle

If niches overlap then species two cannot escape competition from species one

G. F. Gause

Observed that when two species of Paramecium was in a petri dish one always out competed the other to represent CEP

Character displacement

Only traits that aid in reducing competition between species will be selected for

Resource partitioning/ niche differentiation

A change in resource use as a result or character displacement

Random distribution

Individuals have an equal probability of occurring anywhere in an area. No significant interactions are causing individuals to care about placement.  

Ex. Dandelions are wind dispersed

Uniform distribution

Individuals are uniformly spread throughout a distribution. This can be because of minimal resources or territorial behavior.  

Ex. Creosote bush is allelopathic, meaning it exudes chemicals into surrounding soil to inhibit other plant growth 

Clumped distribution

Individuals live in areas of high local abundance and separated by areas of low abundance. May be because seeds do not spread far, or animals travel in packs

Ex. Karner blue butterflies found on wild lupine, which is a flower growing in clumps 

semelparous

One reproductive event 

iteroparous

Many reproductive events 

X

Life stage

Nx

Number of individuals alive at life stage X

Lx

Proportion of original cohort alive at start of life stage x

Mx

Average number of offspring produced by life stage x

Lxmx

Net reproductive rates for each life stage

R0

Net reproductive rate, the sum of all lxmx values

George E. P. Box

Claimed that “all models are wrong, but some are useful”

Ronald Fisher

Invented ANOVA

Nt=No λ^t

Geometric growth model

Geometric growth

Displayed by bacteria and insects that reproduce rapidly

Exponential growth

for species with continuous reproduction and overlapping generations 

Logistic growthSituations where populations have a disproportionally low rate of growth when their density is low

Takes account of resource depletion as populations get larger

Allee effects

Situations where populations have a disproportionally low rate of growth when their density is low

Noe^rt=Nt

Exponential growth model

dN/dt=rN((K-N)/K)

Logistic growth model

Generation time

Time it takes in a pop. to go from egg to egg, seed to seed, etc.

T=(Σxlxmx)/R0

Generation time equation

Ln2/r=tdouble

doubling time equation

reinforcement

Selection for own traits because of existing biases

allopatric distribution

two populations seperated

parapatric distribution

two populations are separated but adjacent to each other

sympatric distribution

Two populations undergo speciation in the same area

Inclusive fitness

Total direct and indirect fitness

Kin selection

A bias that individual has as a result of inclusive fitness (ex. drone bees helping queen)