BIO 305 - Exam I

Ernest Haeckle

Unfortunately, Haeckle was infamous for his misinformation. He was an embryologist, and popularized the idea of Recapitulation Theory; “ontology recapitulates phylogeny.” He implied that animals go through similar stages of embryonic development, which is true. 

Johannes Eugenius Warming

A Danish ecologist. The first person to publish a textbook (specifically plant ecology) in the field of ecology.

Arthur Tansley

Student of Warming. Coined the term ecosystem

Stephen Forbes

From Illinois, Forbes had the first legitimate, peer-reviewed publication about ecology in 1887 called The Lake as a Microcosm. Most of his work was done locally in a lake near Madison. 

Ellen Swallow Richards

First woman accepted into MIT. Incredibly influential on the beginnings of home economics, or the ecology of the human home. Lobbied tirelessly for clean water, sewage treatment plants in cities, etc. One of the first people who applied ecology to tangible things that humans do/interact with every day, and one of the first people to apply chemistry to nutritional science. 

G. Evelyn Hutchinson

Was partially responsible for the evolution of ecology from a collection of natural history facts to a rigorous, analytical discipline with a rich body of theory. 

Robert H. MacArthur

Student of Hutchinson. His most famous papers were on warblers and their distributional patterns in the United States. He applied mathematics to ecology, stating that, like any other science, ecology could be studied mathematically.

Proximate Explanations

(Mechanistic) Focuses on immediate, mechanistic causes of a trait or behavior. They explain how an organism functions in response to environmental or physiological factors.

Ultimate Explanations

(Evolutionary) Focuses on the evolutionary and adaptive reasons behind a trait or behavior. They explain why a behavior evolved and how it contributes to an organism’s survival and reproduction over generations.

Alfred Russel Wallace

He collected a bunch of specimens and sold them to collectors and museums for money. In 1858, he drafted a paper that described evolution via natural selection and sent it to Darwin to publish it for him. 

Charles Darwin

The guy behind “On the Origin of Species.”

Jean-Baptise Lamarck

Created the theory of acquired characteristics. He argued that a subset of ungulates from Africa were constantly under pressure to stretch their necks to get to a higher-up food source, and thus, giraffes eventually got their long necks due to generations of frequent stretching. That’s not how that works, of course.

Patrick Matthew

In his book about trees, he accidentally described evolution through natural selection and argued for speciation. 

Ecology

The scientific study of the interactions between organisms and their environment, and how those interactions affect the distribution and relative abundance of organisms. 

ontogeny recapitulates phylogeny

The theory of recapitulation. Haeckle implied that animals go through similar stages of embryonic development.

Transformations

Changes caused by processes that act upon individuals/species/etc. while they are members of the group. 

Why are hot peppers hot? Provide a proximate and ultimate explanation.

Proximate Explanation:

• Hot peppers contain a chemical call capsaicin. which binds to TRPV1 receptors in our sensory neurons.

Ultimate Explanation

• Capsaicin reacts more with the TRPV1 receptors of animals than it does with birds. Birds carry the seeds farther and are therefore the desired devourers of hot peppers.

Baker’s Law

Island flora are statistically more likely to be self-compatible species.

Biological Evolution

Descent with modification. Changes in allele frequencies over time

Natural Selection

Natural selection refers to the nonrandom (i.e., deterministic) process by which biological traits become more or less common in a population as a function of differences in the survival and reproductive output of their bearers.

First Major Mechanism of Evolution

Natural selection.

Second Major Mechanism of Evolution

Mutation.

Third Major Mechanism of Evolution

Genetic drift.

Fourth Major Mechanism of Evolution

Gene flow.

Fifth Major Mechanism of Evolution

Non-random mating.

Relative Fitness

The reproductive success in comparison to other individuals in the same population.

Absolute Fitness

The total number of offspring an individual produces in its lifetime.

First Condition for Evolution via Natural Selection

Trait must exhibit variation.

Second Condition for Evolution via Natural Selection

Variation in the trait must be correlated to survival and reproductive output (i.e., fitness.)

Third Condition for Evolution via Natural Selection

At least some of the variation must be heritable (i.e., must have a genetic basis.)

Natural Selection: Directional

Focuses on one end of the extremes. (mean trait value changes; variation decreases)

Natural Selection: Stabilizing

Focuses on the area between the extremes. (mean trait value stays the same; variation decreases)

Natural Selection: Disruptive Selection

Focuses on both extremes. (mean trait value stays the same; variation increases)

Allopatric Speciation

“Different” “fatherland/homeland”. Two populations that are in different places 

Sympatric Speciation

Two populations that are together. The rarest form, as speciation typically occurs because of distance. 

Parapatric Speciation

“adjacent/next to” Two populations that are right next to each other, but not together.

Genetic Drift

Stochastic. Genetic drift is the random change in allele frequencies in a population due to chance events. Unlike natural selection, which favors traits that enhance survival and reproduction, genetic drift occurs regardless of an allele’s advantage or disadvantage. It is especially strong in small populations, where chance events can have a bigger impact.

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.

How is the strength of genetic drift related to population size?

The strength of genetic drift is inversely related to population size—it is strongest in small populations and weakest in large populations.

Positive Assortative Mating

Occurs when organisms are more likely to mate with organisms that are like themselves in some respect.

Example: Human Height – Taller people tend to marry taller partners, and shorter people tend to marry shorter partners.

Negative Assortative Mating

Occurs when organisms mate with organisms that are different from themselves in some respect.

Example: MHC-Based Mate Choice in Humans and Mice – People and animals often prefer mates with different Major Histocompatibility Complex (MHC) genes, which helps offspring have stronger immune systems.

MHC

Important in terms of our immune response. When there’s a pathogen or foreign substance, it is at the forefront of identifying the pathogen as a danger to your system. 

Phenology

refers to the timing of important ecological or developmental events.

Extremophiles

Organisms that can tolerate harsh conditions.

Niche

The environmental conditions an organism can survive and reproduce in.

Our most recent and commonly used definition of a species’ niche came from…?

G. Evelyn Hutchinson. He defined a niche as an “n-dimensional hypervolume”, where it is the number of environmental factors that are important to the survival and reproduction of a species (Hutchinson 1957).

He first spoke about it orally in a conference in 1957.

Fundamental Niche

Defines the physical and abiotic conditions under which a species might live in the absence of interactions with other species. 

Realized Niche

Refers to the actual niche of a species whose distribution is influenced by biotic interactions such as competition, predation, parasitism, etc.

Competitive Exclusion Principle

if the niches completely overlap between two species, one will be driven to local extinction. 

Character Displacement

referring to the resulting changes that occur in terms of species’ traits.

Niche Differentiation/Resource Partitioning

referring to the overall expectation in a change of resource use.

Random Population Spatial Pattern

an individual has an equal probability of occurring anywhere in an area. There is no pattern.

Uniform Population Spatial Pattern

individuals are uniformly spaced through the environment.

Overdispersed Population Spatial Pattern

individuals live in areas of high local abundance, separated by areas of low abundance.

Allelopathy

any situation in which an organism is exuding chemicals into its external environment that influences the development, growth, and survival of another organism. IT IS NOT A GENETIC THING.

Semelparous Organism

only reproduce once in their life.

Iteroparous

reproduce multiple times in life.

Type I Survivorship Curve

Most individuals survive early and mid-life, with mortality increasing sharply in old age.

Type II Survivorship Curve

Mortality is constant throughout life; individuals have an equal chance of dying at any age.

Type III Survivorship Curve

Most individuals die young, but if they survive early life, they have a high chance of long-term survival.

r/K Selection Model

an ecological theory that describes two different reproductive strategies organisms use to maximize their fitness. It was developed by Robert MacArthur and E.O. Wilson in 1967 and is based on how species evolve in response to environmental conditions.

r-Selected Organisms

• High reproductive rate (high r value, where r = intrinsic growth rate)

• Many small offspring

• Little to no parental care

• Short lifespan

• Early sexual maturity

• High population growth potential, but high mortality

• Adapted to unstable or unpredictable environments

K-Selected Organisms

• Low reproductive rate (close to carrying capacity, K)

• Few large offspring

• High parental care

• Long lifespan

• Slow development and late sexual maturity

• Stable population sizes near carrying capacity

• Adapted to stable environments with intense competition

Life table: X

Life stage the individuals in a population are at.

Life Table: n_x

number of individuals alive at the start of stage X.

Life Table: l_x

proportion of the original cohort alive at the start of stage X.

Equation: n_x / n₀

Life Table: m_x

fecundity during stage X.

Life Table: l_xm_x

net fecundity during stage X.

Equation: l_x x m_x

Life Tables: xl_xm_x

net reproductive rates for each life stage.

Equation: X x l_x x m_x

N₀

Initial population size.

R₀

represents the net reproductive rate (average # offspring produced per individual).

Equation: The sum of the l_xm_x column.

George E. P. Box

George E. P. Box was a British statistician known for his contributions to experimental design, time series analysis, and Bayesian statistics. He is famous for coining the phrase “All models are wrong, but some are useful.”

Ronald Fisher

Sir Ronald Fisher was a British statistician and geneticist, considered one of the founders of modern statistics and population genetics.

N_t = N₀λ

Geometric growth model. Used to determine the population size at a specific time point in the future.

N_t = N₀R₀^t

Geometric growth model. This is just another version of N_t = N₀λ^t, as we typically replace R₀ with lambda. Used to determine the population size at a specific time point in the future.

N_t = N₀e^rt

Predicts population size at a future time.

dN / dt = rN

Model of exponential growth. Describes rate of growth at any time.

r

The intrinsic rate of increase.

Equation: r = ln(λ)

• Remember: ln = e, and lambda is just R₀.

T_double = ln²/r

Doubling time. number generations for a population to double in size.

T = (∑xlxmx)/R0

Generation time. the average amount of time it takes in a population to go from egg to egg, seed to seed, etc.

Logistic Growth

As resources are depleted, population growth slows and eventually stops.

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

Logistic growth model.

Allee Effect

situations in nature where populations have a disproportionately low rate of growth when their density is low.