Ecology

Ecology

The scientific study of the interactions between organisms and the environment

Levels of ecological organization

Biosphere>Ecosystem>Community>Population>Organism

Climate

Long-term prevailing weather conditions in a given area (temperature, precipitation, sunlight, and wind)

Weather

Short-term state of the atmosphere

Biomes

Major life zones characterized by vegetation type

Global air circulation and precipitation patterns, sunlight

Abiotic factors influencing biodiversity, transporting nutrients

Photic zone

sunlit upper layer of water

Aphotic zone

Layer of water that doesn’t receive light - less life

Benthic zone

Lake/ocean bottom

Abyssal zone

Deep part of aphotic zone

Thermocline

Layer of abrupt temperature change

Species distribution

Diversity affected by climate, precipitation, proximity to equator, disturbance

Climate change

Directional change to the global climate that lasts three decades or more

Ethology

Study of animal behavior (the sum of an animal’s responses to external and internal stimuli)

Tinbergen’s four questions

Proximate causation: “how”

Ultimate causation: “why”

Proximate causation

How and when does the trait develop during the lifetime of an individual

How does the trait work

Ultimate causation

How did the trait evolve

Why does the trait persist over evolutionary time?

Fixed action patterns

a sequence of unlearned acts or largely invariant behaviors directly linked to a simple stimulus

Taxis

more or less automatic, oriented movement toward or away from a stimulus

Kinesis

change in activity or turning rate in response to a stimulus

Biological rhythms

circadian rhythms, migration, circannual rhythms

Learning (modification of behavior as a result of experience)

Modification of behavior as a result of experience

Habituation

Loss of responsiveness to stimuli

Imprinting

establishment of a long-lasting behavioral response

Spatial learning

establishment of a memory that reflects the environment’s spatial structure

Associative learning

the ability to associate one environmental feature with another

Cognition

awareness, reasoning, recollection, and judgement

Problem solving

devising a method to face obstacles

Social learning

observing and interpreting behaviors

Polygyny

A single male and many females

Polyandry

A single female and multiple males

Hamilton’s rule

Natural selection favors altruism when rB > C (r=relatedness, B=benefit, C=cost)

Population

Group of individuals of a single species living in the same general area → share the same resources, affected by the same environmental factors

Population ecology

Study of changes in size, density, and distribution of age classes (range of growth + density → can populations recover from losses)

Population density

Number of individuals per unit of area/volume

Dispersion

Pattern of spacing among individuals within the population, can be clumped, uniform, or random

Semelparity

All offspring in one reproductive event, parent dies afterwards, common in invertebrates, salmon, and plants, typically in harsh environments

Iteroparity

Reproduce several times throughout life, low chances of survival for juveniles = repeated reproductions, can be seasonal or continuous, common in mammals, birds, reptiles

Demography

Study of how populations change over time

Life table

Summarizes the survival & reproductive rates of individuals in a specific age-group (cohort) within a population, longitudinal, concentrates on females

Type 1 survival curve

Common in humans and large mammals, few offspring and high parental care, death at old age

Type 2 survival curve

Common in annual plants, rodents, lizards, and birds, survival probability does not change with age

Type 3 survival curve

High death rates for young, a lot of offspring without parental care, those who survive reach old age

Exponential population growth

Potential to expand greatly when resources are abundant

Logistic growth

Per capita rate of population growth approaches zero as population size nears carrying capacity (K)

R-selected species

Selection for traits that maximize reproductive success at low densities

K-selected species

Selection for traits that are advantageous at high densities

Community

Assemblage of populations of various species living close enough for potential interaction

Competition (-/-)

Different species compete for a resource in short supply, can lead to competitive exclusion

Ecological niche

The total of a species’ use of biotic and abiotic resources

Resource partitioning

Differentiation of ecological niches (sharing is caring!)

Fundamental niche vs realized niche

Niche potentially occupied vs. niche actually occupied after resource partitioning

Character displacement

tendency for characteristics to be more divergent in sympatric populations than allopatric of the same species (resource partitioning)

Predation (+/-)

Interaction where one species kills and eats the other

Herbivory (+/-)

A herbivore eats parts of a plant or alga

Symbiosis

dependency relationship where two or more species live in direct and intimate contact with one another

Parasitism (+/-)

A parasite derives nourishment from a host, which is harmed in the process.

Complex parasites

Have more than one host

Mutualism (+/+)

An interspecific interaction that benefits both species (Obligate=one species cannot survive without the other, Facultative=optional)

Commensalism (+/0)

One species benefits and the other is apparently unaffected

Species diversity

Variety of organisms that make up the community

Species richness

total number of different species in the community (how many species?)

Relative abundance

proportion each species represents of total individuals in the community (any dominant species?)

Shannon diversity index

index of diversity based on species richness and relative abundance → H= -(pA*ln(pA)+pB*lb(pB)…)

Higher H = more divers

Trophic structure

feeding relationships between organisms in a community, from producers to top carnivores

Bottom-up model of community organization

Unidirectional influence from lower to higher trophic levels

Top-down model of community organization (trophic cascade model)

control comes from the trophic level above (predators→herbivores→primary producers)

Keystone species

Exert strong control on a community by their ecological niches, not necessarily abundant in a community (yellowstone wolves)

Ecosystem engineers

Cause physical changes in the environment that affect community structure (beavers)

Foundation species

Facilitators that have positive effects on survival/reproduction of other species, abundant or large in size (trees)

Invasive species

introduced to a new environment (usually by humans);

Enemy release hypothesis

Non-native species thrive due to abundance of natural enemies (parasites, predators, etc)

Intermediate disturbance hypothesis

Species diversity is maximized when ecological disturbances occur at intermediate levels of intensity or frequency

Ecological succession

Sequence of community and ecosystem changes after a disturbance

Primary succession

no soil exists when succession begins, pioneer organisms (lichen) are foundational species

Secondary succession

soil remains after a disturbance/disaster

Island equilibrium model

Species richness on islands depends on island size, distance from mainland, immigration, and extinction; levels off at a dynamic equilibrium point. At smaller islands or further from mainland, equilibrium is reached at a lower richness

Smaller islands/islands further from mainland

Equilibrium reached at lower richness

Ecosystem

All organisms living in a community and the abiotic factors with which they interact → energy flow and chemical cycling

Eutrophication

When nutrient status of an ecosystem changes from poor to rich, can cause algal bloom + mass fish and aquatic life die-off

Archaea

Can live in extreme environments (extremophiles, halophiles for saline, thermophiles for heat >100C),

no nuclear envelope, membrane-enclosed organelles, peptidoglycan in cell wall, some membrane lipids, circular chromosome.

Bacteria

Evolve rapidly in response to environmental conditions (mutation, genetic recombination, rapid reproduction through binary fission),

no nuclear envelope, membrane-enclosed organelles, have unbranched hydrocarbons for membrane lipids, have circular chromosome

Eukarya

Have nuclear envelope, membrane-enclosed organelles, unbranched hydroarbons for membrane lipids, no peptidoglycan in cell wall, no circular chromosome

Transformation

A prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment

Transduction

The movement of genes between bacteria by bacteriophages

Transduction

The process where genetic material is transferred between bacterial cells by bacteriophages

Conjugation

The process where genetic material is transferred between bacterial cells (sex pilus)

Bioaccumulation

Toxins build up as you move up trophic levels

Protists

Classified as eukaryotes, polyphyletic group, closely related to plants, animals, and fungi. Often symbiont, producer, or parasite

Supergroups of eukaryotes

Excavata, SAR, Archaeplastida, Unikonta

Classification by ecological role

Algae - photoautotrophic

Protozoa - heterotrophic

Fungus-like - resemble fungi and absorb nutrients

Classification by habitat

Phytoplankton - photosynthetic, float or swim

Zooplankton - heterotrophic, float or swim

Classification by motility

Flagellates, Ciliates, and amoebas

Flagellates

Swim using eukaryotic flagella

Ciliates

“Hairy”, swim with cilia

Amoebas

Move using pseudopodia

Excavata

Phagotrophs that use a “cave” to take other cells in. Often from anaerobic environments. Includes predators, heterotrophs, and mixotrophs. Typically flagellated

SAR

Stramenopila, Alveolates, Rhizarians

Archaeplastida

Includes land plants and several algaes, green and red algae

Unikonta

Includes animals, fungi, and related protists. Amoebozoans!