Option C Ecology

Define Limiting factor

An environmental factor that limits the distribution or numbers in a population

Define Limits of Tolerance

They are the highest/lowest values of abiotic factors that an organism can survive

Define an ecological niche

The mode of living of a species; its use of biotic and abiotic resources.

State two types of niche

fundamental niche and realised niche

Define Symbiosis

An interaction between two species where both benefit.

List five types of interaction between species.

mutualism, parasitism, competition, predation, herbivory

Define a keystone species

a species that has a disproportionately large effect on its environment relative to its abundance

Define food conversion ratio

The percentage of ingested energy converted to biomass.

Name two types of ecosystems

closed (e.g. aquarium) and open

Define biome

a geographical area that has a particular climate and sustains a specific community of plants and animals

What are the two main abiotic factors in biomes?

rainfall and temperature

What is the Gersmehl diagram

it is a diagram that shows the differences in nutrient flow and storage between different types of ecosystems

Name three stores on nutrients in ecosystems.

In biomass, litter, or soil.

Define Primary succession

ecological succession on entirely new lands without any established soil (due to events such as volcanic eruptions)

Define ecological succession

the process by which a sequence of increasingly complex communities develop over time

Define secondary succession

occurs when succession starts on existing soil following a natural artificial disturbance

Define endemic species

species that are native to a defined geographic region

Define alien species

species that have been transferred from their natural habitat to a new ecosystem.

Define invasive species

plants and animals that have migrated to places where they have a tendency to spread causing damage to the environment, human economy and or human health

Define competitive exclusion

The idea that two species cannot occupy identical niches within a community, one will exclude the other.

Name an Australian example of an invasion species.

The cane toad (or European rabbit)

Define biomagnification

the process in which chemical substances become more concentrated each trophic level

Define microplastic

small plastic debris

Define indicator species

An organism used to assess a specific environmental condition. It usually has a limited range of tolerance to that condition.

Name an example of an indicator species.

mayfly nymph (dissolved oxygen levels in rivers), lichens (air-borne pollutants)

Define biotic index

A calculated measure used to compare the relative health of two or more locations

Define biodiversity

A measure of the number and variety of organisms found within a specified ecosystem.

Purpose of Simpson's reciprocal index

It measures the relative biodiversity

Formula for Simpson's reciprocal

total number of organisms of all species ( total no. of organisms of all species - 1 ) / sum of all species x no. of single species (no. of single species - 1 )

List four biogeographic factors which can affect biodiversity.

Size of the conservation area (large is best), edge effect (less edge is best), isolation (close to other nature reserves is better), corridors (provide habitat to connect areas)

Define in situ conservation

The preservation of species within their natural habitat

Define ex situ conservation

the preservation of plant and animal species outside their natural habitat, in zoos or reserves.

advantages for ex situ conservation

allows for greater control of essential conditions ( eg : climate control, dietary intake) + increases chances of breeding successful by utilising artificial methods (eg : IVF)

disadvantages for ex situ conservation

increases interbreeding by restricting the gene pool and restricts the evolution of the species + does not prevent potential destruction of their natural habitat + less likely to be successful reintroduced into the wild which results in the loss of autonomous survival

Define population

all the individuals of a given species living in the same area at the same time

Name a method used to estimate the population of a mobile species.

capture-mark-release-recapture

Name two types of population growth

exponential growth and logistic growth

List the phases of the Sigmoid growth curve

Lag phase, exponential growth phase, transitional phase, plateau

Describe lag phase

population growth will be slow as there are few reproductive individuals that are likely widely spread

Describe exponential phase

as number increases, there is a rapid increase in population size as natality exceeds mortality. Mortality is low because there are abundant resources and minimal environmental resistance.

Describe transitional phase

as population increases, resources become limited which results in increase competition for survival. As natality decreases and mortality increases, the population growth becomes slower.

Describe plateau phase

mortality rates = natality rates and population growth becomes static. population has reached the carrying capacity (k) of the environment, with limiting factors keeping the population stable. population at this point will not be constant, but will oscillate around the carrying capacity to remain even.

Name two classifications of limiting factors.

Top down control and bottom up

Define top down control

population growth pressures applied by other organisms at higher trophic levels

Define bottom up control

factors that limit population growth by affecting resources or lower trophic levels

Define sustainable yield

the amount of natural resources that can be taken from an ecosystem without reducing the base stock

Define maximum sustainable yield (MSY) in fishing

in fishing, the MSY is the highest proportion of fish that can be removed from the total population without jeopardising the maximum yield in the future - it represents the optimum balance between reproductive growth rates and losses to harvesting and death

List three methods to estimate commercial fish stock

capture-mark-release-recapture, echo location, analysis of fish data

Name three factors that need to be taken in for sustainable fishing practices

population size, reproductive status, age

Name bacteria involved in the nitrogen cycle.

Rhizobium, Azotobacter, Nitrosomonas, Nitrobacter, Pseudomonas denitrificans

Outline how water-logged soil affects the nitrogen cycle?

It decreases oxygen levels creating anoxic conditions favoured by denitrifying bacteria whch convert nitrates to nitrogen gas.

What is the phosphorus cycle

the movement of phosphorus atoms from rocks through the biosphere and hydrosphere and back to rocks via the process of chemical weathering

Define eutrophication

The nutrient enrichment of a body of water

Ecological consequences of eutrophication

Increased availability of nutrients --> increased growth of Algae --> Bacterial decomposition removes oxygen from water.