Unit 8 Ecology

Ethology

the study of how evolutionary processes shape inherited behaviours and the ways animals respond to specific stimuli

Behaviour

an animal’s response to a stimulus

Proximate cause

What was the stimulus to cause the behaviour?

Ultimate cause

How does the behaviour help the animal survive and reproduce?

Fixed Action Patterns

a sequence of unlearned acts directly linked to a stimulus

Migration

the regular, long-distance change in location

Signal

a stimulus generated and transmitted from one animal to another

Pheromones

chemicals emitted by members of a species that can affect other members of the same species

Stimulus response chains

when a response to a stimulus serves as the next stimulus for a behaviour

Directed movements

movements towards or away from a stimulus

Kinesis

a change in the rate of movement or the frequency of turning movements in response to a stimulus, non-directional

Taxis

directional movement towards (positive) or away from (negative) a stimulus

Phototaxis

Movement in response to light

Chemotaxis

movement in response to chemical signals

Geotaxis

movement in response to gravity

Learning

a modification of behaviour based on specific experiences

Imprinting

a long lasting behavioural response to an individual

Spatial learning

establishing memories based upon the spatial structure of the animal’s surroundings

Associative learning

the ability to associate one environmental feature with another

Social learning

learning through observations and imitations of the observed behaviours

Foraging

food obtaining behaviour that involves searching for and exploiting food resources

Mating behaviours

animals can be monogamous or polygamous

Atruism

selfless behaviour that benefits others, often at a cost to oneself

Phototropism

a directional response that allows plants to grow towards a source of light

Photoperiodism

allows plants to develop in response to day length: plants flower at only certain times of the year

Physical defences

thorns, trichomes, etc

Chemical defences

production of toxic or distasteful compounds

Ecosystem

the sum of all the organisms living in a given area and the abiotic factors they interact with

Biotic

living, or once living, components of an environment

Abiotic

nonliving (physical and chemical properties) of the environment

1st Law of Thermodynamics

energy can neither be created nor destroyed, only transferred

Law of Conservation of Mass

chemical elements are continually recycled in the environment

2nd Law of Thermodynamics

exchanges of energy increase the entropy of the universe

Metabolic rate

the total amount of energy an animal uses in a unit of time

Endotherms

use thermal energy from metabolism to maintain body temperatures

Ectotherms

use external sources to regulate their body temperatures

Heterotrophs

rely on autotrophs because they cannot make their own food

Autotrophs

use light energy to synthesise organic compounds

Primary consumers

herbivores

Secondary consumers

carnivores that eat herbivores

Tertiary consumers

carnivores that eat carnivores

Decomposers

get energy from detritus (nonliving organic materials)

Food chain

the transfer of food energy up trophic levels

Food webs

Linked food chains

Primary production

the amount of light energy that is converted to chemical energy

Gross primary production (GPP)

total primary production in an ecosystem

Net primary production (NPP)

the GPP minus the energy used by the primary producers for respiration (R_a)

Secondary production

the amount of chemical energy in a consumer’s food that is converted to new biomass

10% rule

the transfer of energy between trophic levels is around 10% efficiency

Water cycle

water is essential for all life and influences the rate of ecosystem processes

Carbon cycle

carbon is essential for life and required in the formation of organic compounds

Nitrogen cycle

nitrogen is important for the formation of amino acids, proteins, and nucleic acids

Phosphorous cycle

phosphorous is important for the formation of nucleic acids, phospholipids and ATP

Population

a group of individuals of the same species living in an area

Population ecology

analyses the factors that affect population size and how and why it changes over time

Dispersion

the pattern of spacing among individuals within a population

Clumped

individuals gather in patches

Uniform

evenly spaced individuals in a population (can be due to territoriality)

Random

unpredictable spacing, not common

Demography

the study of the vital statistics of populations and how they change over time

Life table

an age-specific summary of the survival pattern of a population, represented by a survivorship curve

Type I curve

low death rate during early/middle life and high death rate later in life

Type II curve

constant death rate over the lifespan of the organism

Type III curve

high death rate early in life and lower death rate for those that survive early life

Per capita rate of increase formula

dN/dt = B - D, where dN/dt is the change in population size, B is the birth rate, and D is the death rate per capita.

Exponential growth model

a population is living under ideal conditions, population grows rapidly

Exponential growth formula

dN/dt = r_maxN, where rmax is the maximum per capita growth rate, and N is the current population size (J shaped curve

Logistic growth model

the per capita rate of increase approaches zero as the population size nears its carrying capacity

Logistic growth formula

dN/dt = r_maxN(K-N/K) where K is the carrying capacity, and N is the current population size and r_max is the per capita growth rate

Life history

the traits that affect an organism’s schedule of reproduction and survival, including age at first reproduction, frequency of reproduction, and number of offspring produced

K-selection (density dependent)

selection for life history traits that are sensitive to population density, seen in high density populations that are close to carrying capacity

R-selected (density independent)

selection for life history traits that maximise reproductive success, seen in low density populations with little competition

Density-dependent regulation

as a population increases, factors can slow or stop growth by decreasing birth rate and increasing death rate (competition, predation, toxic wastes, territoriality, disease, intrinsic factors)

Density-independent regulation

factors that exert their influence on population size, but the birth/death rate remains the same (weather, climate, natural disasters)

Community

a group of populations of different species living closely and capable of interacting

Habitat

a place or part of an ecosystem occupied by an organism

Ecological niche

the role and position a species has in its environment

Fundamental niche

the niche potentially occupied by the species if there were no limiting factors (predators, competitors, etc)

Realized niche

the portion of the fundamental niche the species actually occupies

Interspecific interactions

interactions of individuals from one species with individuals of another species

Competition

-/- relationship where individuals of different species compete for limited resources

Competitive exclusion principle

two species competing for the same resource cannot coexist permanently

Niche partitioning

natural selection drives competing species into different patterns of resource use, or different niches

Predation

+/- relationship where one species (predator) kills and eats the other species (prey)

Cryptic coloration

camouflage

Batesian mimicry

harmless species mimics a harmful one

Mullerian mimicry

two or more bad-tasting species resemble each other

Herbivory

+/- relationship where one organism eats part of a plant or alga

Symbiosis

when 2 or more species live in direct contact with one another

Parasitism

(+/-) when one organism (parasite) derives nourishment from another (host)

Mutualism

(+/+) when both organisms benefit from the relationship

Commensalism

(+/0) when one organism benefits and the other is neither harmed nor benefited

Facilitation

(+/+ or 0/+) when one species has a positive effect on the survival and reproduction of another without intimate association of symbiosis

Species diversity (biodiversity)

the variety of different organisms within a community

Species richness

the number of different species

Relative abundance

the proportion each species represents of all the individuals in the community

Simpson’s diversity index

calculates diversity based on species richness and relative abundance, high diversity index means high biodiversity; low diversity index means low biodiversity

Simpson’s diversity index formula

Diversity index = 1-∑(n/N)² where n is the number of individuals of a species and N is the total number of individuals of all species

Invasive species

non-native species that disrupt ecosystems and outcompete native species

Keystone species

not usually abundant, but other species in an ecosystem rely on them because of their important ecological niches