Unit 5: Ecology

Define limiting factor

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.

There are two types: fundamental niche and realised niche

Define symbiosis

An interaction between two species where both benefit.

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

Two main abiotic factors in biomes

rainfall and temperature

Gersmehl diagram

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

Three stores of 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

Examples of invasive species

1. Cane Toad

2. European Rabbit

European Rabbit

24 European rabbits exploded in number and are regarded as Australia's worst vertebrate pest

• they thrived due to abundance of food and lack of natural predators (as well as a rapid reproduction cycle)

Define biomagnification

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

Define microplastic

small plastic debris <1mm in size

Define indicator species

an organism used to assess a specific environmental condition; usually has a limited range of tolerance to that condition

Example of an indicator species

Lichens are composite organisms made up of fungi and algae in a mutualistic relationship.

They act as indicators of air pollution, especially sulfur dioxide, a waste product of the burning of sulfur-containing fossil fuels.

Depending on the species of lichen, various levels of sulfur dioxide are tolerated.

The bushy beard lichen is unable to tolerate even low levels of sulfur dioxide within the atmosphere. Therefore, if this lichen is absent it may indicate high levels of sulphur dioxide.

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

Simpson's reciprocal index

measures the relative biodiversity

• D = diversity index

• N = total number of organisms of all species

• n = number of individuals of a particular species

• ∑ = sum the values for each species

Four biogeographic factors, affecting biodiversity

1. Size of the conservation area (large is best)

2. Edge effect (less edge is best)

3. Isolation (close to other nature reserves is better)

4. 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 of ex situ conservation

1. allows for greater control of essential conditions (eg: climate control, dietary intake)

2. increases chances of breeding successfully by utilising artificial methods (eg : IVF)

Disadvantages for ex situ conservation

1. increases interbreeding by restricting the gene pool and restricts the evolution of the species

2. does not prevent potential destruction of their natural habitat

3. 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

Method used to estimate the population of a mobile species

capture-mark-release-recapture

Two types of population growth

1. Exponential Growth - impossible as there will always be factors affecting the growth rate of a population

2. Logistic Growth

Phases of the Sigmoid growth curve

1. Lag phase

2. Exponential growth phase

3. Transitional phase

4. 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

1. Top down control

2. 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

The maximum sustainable yield is the largest amount of fish that can be caught without causing the population to fail.

List three methods to estimate commercial fish stock

1. capture-mark-release-recapture

2. Echo location

3. Analysis of fish data

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

1. population size

2. reproductive status

3. age

Name bacteria involved in the nitrogen cycle

1. Rhizobium + Azotobacter →nitrogen-fixing bacteria

2. Nitrosomonas + Nitrobacter → nitrifying bacteria

3. Pseudomonas →denitrifying bacteria

Nitrogen Cycle

Outline the effects of water-logged soil on the nitrogen cycle

The anaerobic environment promotes denitrification by Pseudomonas denitrificans.

This depletes nitrates in the soil, which significantly reduces plant growth, as the fertility of the soil decreases.

Areas that are waterlogged for long periods of time have nitrogen-deficient soils.

Plant adaptions to waterlogged soil

Some plants have adapted to obtaining nitrogen by digesting animals.

For example, some plants use pitfall traps to lure insects with nectar. Their inner lining is slippery, so insects fall in and are broken down by digestive enzymes.

Phosphorus Cycle

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

Steps of the Phosphorus Cycle

1. The weathering of phosphorite, sedimentary rock containing large quantities of phosphorus in the ocean, releases the phosphate ions and other minerals into the soil and water.

2. The phosphate ions and associated minerals are readily taken up by plants, which are consumed by animals. The phosphate is incorporated into organic molecules such as ATP or DNA.

3. After the plants and animals die, the phosphate is released back into the soil and water.

4. After the phosphate has been released back into the soil or water, it may be recycled and taken up by new plants.

Phosphorus in the soil can be washed into the waterways and ends up in the oceans through a process called leaching. Once the phosphate finds its way into the oceans, it can be thousands of years before it returns to the land as it is recycled within the ocean food webs or held within the sediments on the ocean floor. 

Define eutrophication

The nutrient-enrichment of waterways and streams caused by leaching and/or the release of untreated sewage

Ecological consequences of eutrophication

• Nutrients encourage the growth of algae on the water surface

• Algal blooms black light to water plants below them

• If the algae and plants die, bacteria feed on them and use up oxygen, causing a higher BOD

• The reduced levels of oxygen lead to the death of sensitive organisms, such as invertebrates and fish

Density-dependent Factors

competition for limited resources available within an area such as the availability of food, habitats or fending off/hiding from predators

Most vulnerable = young, old, weak

Density-independent Factors

the environment in which the animal lives and such things as a harsh and cold winter or a dry summer, which can impact numbers as the population struggles to survive

Most vulnerable = everyone is affected (though weaker organisms will die first)

ecological niche

the distinct role a species plays in its ecosystem

generalist species

broad niche - has a lot of different things it can eat (cockroaches)

specialist species

specific niche - specific to environmental change (salamanders)

indicator species

sensitive to environmental change (lichen)

keystone species

large role in maintaining the balance of the ecosystem (starfish)

foundational species

an animal that enhances the habitat to benefit others

in-situ conservation

protected on nature preserves or national parks and they stay in their natural habitat (national park)

ex-situ conservation

species are removed from their natural habitat (captive breeding)

edge effect

change in the ecosystem on the edge of a reserve or parks

fragmentation

some reserves become fragmented into smaller patches, usually by conservation

island size

a larger reserve is better ecologically than a smaller one

fundamental niche

represents the broadest possible niche a species could potentially live in within the boundaries of its limiting factor

realized niche

represents the actual mode of existence in which the species is really found

biotic index

measures the health of an environment by counting the number and type of organisms int he environment

limiting factor

any factor that puts an upper limit one the size of a population

FCR

Feed Conversion Ratio: the ratio of food mass provided to body masss output

closed ecosystem

energy can go in and out, but matter cannot

reasons why energy is lost between trophic levels

1. not all biomass is eaten in one trophic level and is broken down by decomposers

2. some of the biomass is indigestible and egested

3. some of the biomass exits the body as urine

4. energy is lost through cellular respiration

gersmehl nutrient cycle

a graphical representation of how biomass, litter, and soil interconnect to recycle nutrients for the plants and animals in the ecosystem

primary succession

when the area that is colonized arises from a lifeless area

secondary succession

soil remains following an upheaval of expected change within an ecosystem that is undergoing succession

interspecific competition

individuals of one species compete within those of a different species

intraspecific competition

organism compete with others of the same species for things such as food or a mate

predator/prey

a predator is an organism that feeds on another living species, that other species being the prey (mantis/cricket)

herbivory

primary consumers feed only on plant material

parasitism

when one organism feeds on or off another and does harm to the other

mutualism

a relationship in which both organisms benefit

commensalism

a relationship when one organism benefits and the other is unaffected

transect

a line across a habitat or part of a habitat which is used to explore a relationship between the population of organisms present and one or more abiotic factors

poikilotherms

an animal that has a variable body temperature according to the surrounding environment

homeotherms

an animal which maintains a regulated body temperature through physiological mechanisms

gersmehl diagram - L

the total amount ’organic’ matter, including humus and leaf litter

gersmehl diagram - B

the total mass of living organisms, mainly plant tissue per unit area

gersmehl diagram - S

the mineral (inorganic) and organic nutrients that are found in the soil

gersmehl diagram

diagrams used to model how biomass, litter, and soil interconnect to recycle nutrients for the environment

alien species

a species of plant, animal, or microorganism that moves to an area in which is did not previously occur

biological control

controlling invasive species by introducing predators or diseased organisms

physical removal

controlling invasive species by physically removing them

chemical control

controlling invasive species by using herbicides, pesticides, insecticides or other poisons

bioaccumulations

when organisms accumulate toxins in their body by consuming other organisms with toxins

biomagnification

when the concentration of toxins increases with each trophic level as you go up the food chain because the organisms are consuming a large number of organisms in the trophic level below them

ocean gyre

a naturally occurring ocean current