Option C: Ecology and Conservation

Population

A group of organisms of the same species that live in the same area at the same time.

Community

A group of populations living and interacting with each other in an area.

Ecosystem

A community and its abiotic environment.

Limiting Factor

The factor that is most scarce in relation to an organism's needs.

Plant Limiting Factors

Temperature, water availability, light intensity, soil pH, soil sanity, and availability of mineral nutrients

Animal Limiting Factors

Temperature, water, breeding sites, food supply, territory.

Transect

A method used to ensure that there is not a bias in student's selection of a sample and it can be used to correlate the distribution of a plant or animal species with an abiotic variable.

Ecological Niche

The sum total of a species' use of the biotic and abiotic resources in its environment.

The Fundamental Niche

Represents the broadest possible niche a species could potentially live in within the boundaries of its limiting factors or zones of intolerance, with no external pressures such as competitors or interactions with other species. The idea of the fundamental niche is very much theoretical.

The Realized Niche

Represents the actual mode of existence in which the species is really found, taking into account its zone of intolerance as well as all interactions with other species.

Competitive Exclusion Principle

When two species occupy fully overlapping niches, the one with the greater selective advantage will out-compete the other, leading to its extinction from that environment.

Interspecific Competition

When individuals of one species compete with those of a different species.

Local Examples of Interspecific Interactions

Dodder --> Parasitism (invades plant tissues and obtains nutrients and support from them)
Fire coral and Hawkfish --> Commensalism (fish gains protection from coral without harming it)
Bagworm Moth --> Herbivore
Bahama woodstar and flowers --> Mutualism (Bird gains nectar while plant is assisted in pollination)

Intraspecific Competition

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

Predator

An animal that hunts other animals for food

Prey

An organism that is killed and eaten by another organism

Herbivory

Interaction in which one animal (the herbivore) feeds on producers (such as plants)

Parasitism

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

Mutualism

A relationship exists in which both parties benefit

Commensalism

Occurs when one organism benefits and the other is unaffected.
Ex: Hawkfish and fire coral

Keystone Species

A species that exerts a strong control on community structure without necessarily being abundant in number.
Example: Pisaster sea star

Removal of Keystone Species

- Increase in certain species
- Increase in competition- Wiping out of certain species
- Emigration of some species
- Species diversity decreases (sometimes)

Endemic Species

species that are native to an area

Alien Species

species that have been transferred from their natural habitat to a new environment where conditions are still suitable for their survival

Invasive Species

Species that increase in number and spread rapidly; have a detrimental effect on native food chains.

Effects of Invasive Species

- Extinction of some native species
- Introduction of diseases
- Increased competition
- Reduction in number of endemic species
--> Excessive predation
--> Interspecific competition due to niche overlap

Alien Species Case Studies

- Cane toad in Australia:
--> Introduced to control the cane beetle
--> Toad became a generalist predator and competitor for food resources
- Zebra Mussel in North America
--> Can clog pipes, municipal water systems, etc.

Methods to Control Alien Species

- Eradication programs
- Biological control

Eradication programs

Application of herbicides and selective harvesting of invasive plants as well as trapping and culling invasive animals. (Ex: removing of invasive mammal species from islands- Norway rats in NZ)

Biological Control

the use of a predator, parasite or pathogen to reduce or eliminate a pest

Biomagnification

The process by which toxins become more concentrated at each successive trophic level.

Bioaccumulation

The process by which toxins build up in the bodies of organisms.

DDT (dichlorodiphenyltrichloroethane)

A colorless odorless water-insoluble crystalline insecticide C14H9Cl5 that tends to accumulate in ecosystems and has toxic effects on many vertebrates; became the most widely used pesticide from WWII to the 1950's; implicated in illnesses and environmental problem; now banned in US.

Benefits of DDT Use

- Indoor spraying against malaria
--> Reduces malaria cases

Risks of DDT Use

- Ecological pollution
- Biomagnification
- Human health risks

Plastics in the Ocean

Macro and micro plastic debris have accumulated in marine environments
--> Release of organic chemicals that can bioaccumulate and biomagnify
--> Plastics absorb organic chemicals thus concentrating toxins
--> Animals eat/become tangled in plastic pollution
--> Laysan Albatross

Macroplastics

large visible debris including nets, bucket, and trash that has not degraded

Microplastics

Small pieces of plastic that has been broken down through chemical or physical degradation. Harder to see, but accounts for 65% of all ocean debris.

Gyre

a circular motion of water in each of the major ocean basins

Food Web

A community of organisms where there are several interrelated food chains

Trophic Level

The position an organism occupies in a food chain

Community

A group of different species that occupy the same location at the same time.

Biome

A large community of plants and animals that occupies a major habitat or region, e.g. rainforest, desert.

Biomass

Total amount of living tissue within a given trophic level

Feed Conversion Ratio (FCR)

A measure of the efficiency of an animal's ability to convert feed mass into increased body mass.

Mass of food consumed (kg)/body mass gain (kg).

Whittaker climograph

A graph showing the relationship between temperature, rainfall and ecosystem type

Poikilotherm

An animal which has a variable body temperature according to the surrounding environment

Homeotherm

An animal which maintains a regulated body temperature through physiological mechanisms.

Egestion

The removal of undigested material from the body (feces).

Excretion

The removal of the waste products of metabolic reactions (carbon dioxide/cellular respiration and urea/de-amination of amino acids).

Gersmehl nutrient cycle diagrams

A model of the cycling of nutrients within an ecosystem.
They were first devised by P. F. Gersmehl in 1976, hence the name.
Shows the inter-relationships between nutrient stores and flows.

Primary Succession

An ecological succession that begins in an area where no biotic community previously existed
Moss and Lichens are the first species to appear and they can create a layer of soil (through decomposition) for other species to emerge.

Secondary Succession

Succession following a disturbance that destroys a community without destroying the soil

Effect of an Environmental Disturbance on an Ecosystem

Change in:
- Species diversity
- Stem density
- Above ground biomass
- Leaf area index
- Volume of leaf litter
- Water cycle variables including infiltration rates and run-off rates
- Soil variables including soil structure, soil moisture, soil nutrient levels, and compaction levels
- Light levels- Bulk soil density

Net Production Calculation

net production (plants) = gross production - respiration [units are kJ m-2 yr-1]

When is an equilibrium reached?

When total community production to total community respiration (P/R) ratio equals to 1 --> ecosystem has reached a relatively stable stage.

Closed Ecosystem

An ecosystem in which no materials can leave or enter, but through which energy from external sources can flow.

Open Ecosystem

Exchange matter and energy with their surroundings (Ex: natural systems). Undisturbed: the rate of exchange of matter with the surroundings occurs most notably due to the water cycle and nutrient cycles that have a gaseous phase. Human interference increases the exchange of matter

Indicator Species

A species that is present only when specific environmental conditions are met. Examples include:
- Moss
- Coral
- Mayfly Larva

Biotic Index

A value derived from a large range of species (indicator species) that have varying degrees of tolerance to a particular abiotic factor, e.g. water pollution or air pollution.

In situ Conservation

Involve endangered species remaining in the habitat to which they are adapted --> conserve more aspects of the organism's niche.
= Establish a nature reserve
= Active management: controlled grazing, removal of shrubs and trees, limiting predators, feeding the animals, etc.

Ex situ Conservation

Involve removal or organisms from their natural habitat. --> Used to back up in situ conservation measures

Conservation of Biodiversity

The preservation of species involves international cooperation through intergovernmental and non-governmental organizations.

Components of Biodiversity

- Richness = number of species present
- Evenness = how close in number each species is

Simpson Diversity Index

Quantifies biodiversity- richness and evenness (greater biodiversity=higher value of D)
- D=N(N-1)/Sum n(n-1)
--> N=total number of organisms of all species found
--> n=number of individuals of a particular species

Biogeography can influence Diversity

- Large nature reserves=more biodiversity
- Connected nature reserves= more effective at preserving biodiversity
- Circular reserve=better

Impact of Island Size and Edge Effects on Diversity

- Proximity to mainland =new colonization
- Small island =extinction will be higher, small population size, low genetic diversity

Edge Effect

The condition in which, at ecosystem boundaries, there is greater species diversity and biological density than there is in the heart of ecological communities.

When biologists wish to determine the population of a species within an area, they have one of two options:

- Count every animal.
- Count a sample of the animals present and estimate the total number.

Point Sampling

The study area is mapped out and a grid drawn over it. Random points are generated within the grid and sampling is taken as close to those points as possible.

Transect Sampling

Line transect
- A transect line is rolled out over the study area. At regular intervals a sample is then taken. A line transect generally measures presence only.

Belt transect
- Two transect lines are rolled out and the presence and abundance of species that lie between them are recorded.

Quadrat Sampling

The study area is mapped out into a grid of squares and some are chosen at random. Within those squares the presence and abundance of species are recorded.

Mark and recapture (The Lincoln index)

Within the study area a portion of a population is captured, marked and then released.
At a chosen time, a second capture is carried out and the number of those from the previous capture is recorded. Using a mathematical formula, the population number is estimated.

Lincoln Index Formula

Population Size (N) = n1 x n2/n3

N = total population size of animals in the study site

n1 = number of animals captured on the first day = number of animals marked

n2 = number of animals captured on the second day

n3 = number of marked animals recaptured on the second day

Overfishing

When fishermen remove fish from the seas at a rate that is greater than the rate at which fish reproduce.

Underfishing

When fishermen remove fish at a rate that is less than the rate at which fish reproduce.

Maximum Sustainable Yield

The maximum rate at which a renewable resource can be exploited without impairing its ability to be renewed or replenished

Strategies for Sustainable Fishing

- Established quotas to ensure that there is a maximum mass of fish caught.
- Exclusion zones to protect vulnerable areas and allow fish the opportunity to breed safely.
- Closed seasons in which no fishing is allowed. This gives fish the opportunity to breed and a chance for the population to re-establish themselves.
- Restriction of net size so that excessively large nets are not allowed. Also, enforcement of large mesh sizes so that the younger fish are able to swim through the nets and continue to grow and breed before being caught.
- Ensuring that juvenile fish are allowed to grow and breed before capture. This can be achieved by determining the relationship between the age of fish and their size.

J Shaped Growth Curve

The maximum rate at which a population can increase given ideal conditions and unlimited resources (things it needs to use) is called its biotic potential (Intrinsic rate of increase [r]). Factors that determine the biotic potential of an organism include its fertility rate, generation time and size. These factors are in-built and non-environmental.

S Shaped (Sigmoid) Growth Curve

Exponential growth does not continue forever; eventually, density-dependent factors such as food availability, space, disease, predators and possibly toxic waste products produced by the organisms will set limits to population increase.

Carrying Capacity (K)

The maximum population that the environment can indefinitely sustain.

Natality (N)

birth rate

Immigration (I)

Migration to a new location

Mortality (M)

death

Emigration (E)

Migration from a location

Equilibrium in a Population is Reaching When:

N + I = M + E.

Top Down Limiting Factor

- Population growth of species within a food web is affected by the number of consumers and predators and the rate at which they graze or consume prey.
- If there is a reduction in grazing fish through human impact (fishing) then top-down limiting factors are affected and once again, algal blooms can occur.

Bottom Up Limiting factors

- Controls of population density from resources such as light or nutrients for plants and prey organisms for animal.
- If nutrient enrichment occurs through human activities such as fish farming, application of fertilizer on nearby fields or through sewage outflows into the sea, then bottom-up limiting factors are affected through the forming of algal blooms and eutrophication occurs.

Nitrogen Cycle

The transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere

Nitrogen Fixation in Free Soil

- N2 -> NH3
- Azotobacter are free-living bacteria that can be found within soil.

Mutualistic Nitrogen Fixation

- N2 -> NH3
- Rhizobium are NOT free-living bacteria, cannot be found loose within the soil and must form root nodules with plants called legumes.

Abiotic/Industrial Nitrogen Fixation

- N2 -> NH3
- Production of fertilizer using the Haber Process
- Lightening striking atmospheric Nitrogen

Nitrification (1st)

Ammonia to Nitrites
NH3 -> NO2
Nitrosomonas (Bacteria)

Nitrification (2nd)

Nitrites to Nitrates
NO2 -> NO3
Nitrobacter (bacteria)

Uptake

Nitrates are actively transported into the roots of plants using ATP for energy

Assimilation

- Plants use nitrates to make their own proteins
- Animals feed on plants, digest and rearrange proteins to make their own proteins

Death and Excretion

The waste production of digestion and dead bodies of plants and animals are full of molecules containing nitrogen.

Decomposition

- Decomposers such as bacteria and fungi break down complex proteins and release Nitrogen gas into atmosphere.
- Proteins -> N2

Denitrification

- NO2 & NO3 -> N3
- Bacteria remove nitrates and nitrites and put nitrogen gas back into atmosphere
- Pseudomonas denitrificans (bacteria)

Phosphorus Cycle

The movement of phosphorus atoms from rocks through the biosphere and hydrosphere and back to rocks.