IB Biology HL - Option C - Ecology

ecological niche

role of the species e.g

\
spatial habitat - where the species lives

interactions - how the species afects and is affected by otherspecies in the community, including nutrition

\

competitive exclusion principle

\

only one species can occupy a niche in an ecoysystem

\

fundamental niche

\

Niche that a species could potentially occupy

\

realized niche

the niche that a species actually occupies

competition

a species using a resource reduces the abailible amount to other species using it. It is the reason for differences between fundamental and realized niche

keystone species

essential for ecosystem and has a significant effect on the structure of an ecological community.

\
e.g Tree is direct food source for most species in the forest community

e.g Predator has major effect on population sizes by limiting the number of their pray

transect

method of sampling - to investigate whether the distribution of a species is correlated with an **abiotic variable**

Herbivory (interaction)

primary consumers feed on plants or other producers; this harms producers but reduces competition between producers.

predation (interaction)

predators benefit as they feed on prey.

Parasitism (interaction)

a parasite that lives on/in a host, obtaining food from the host and harming it.

Mutualism

Different species live in a close relationship where they both benefit.

Mutualism Example (Reef Building Corals)

Coral and Algae (zooxanthellae) shared mutualistic relation (Also Symbiotic).

\
1) Coral provide algae with a protected environment close to light for photosynthesis

2)Zooxanthellae provide coral with products of photosynthesis: glucose, amino acids, oxygen

3)Coral Waste Products (ammonia, carbon dioxide, phosphate) used by zooaxanthellae

Symbiotic

Both different species live together

Gross production

Total amount of energy in food - eaten by animal/made by photosynthesis (in producers)

Net Production

is the amount of energy converted to biomass in an organism. It is always less than gross production because some food is used in cell respiration and the energy released from it is lost from the organism and the ecosystem

Feed Conversion ratio

Conversion Ratio = intake of food (g) ÷ net production of biomass (g)

\
(Note: Higher the ratio, the lower percentage of ingested energy that is converted to biomass (g))

Why do birds and mammals have a high respiration rate?

to maintain constant body temperatures

Food Chain

A single sequence of organisms, each of which consume the previous one in a chain

Food Web

A diagram used to show all possible food chains in a community

Nutrients

Retained in ecosystem for an unlimited time.

Closed ecosystem

An ecosystem that does not exchange nutrients with its surroundings.

terrestrial ecosystems

three main storage compartments: biomass (living organisms), litter (dead organic matter) and the soil

open ecosystem

nutrients also flow to or from the compartments and the surroundings

A Gersmehl diagram

a model of nutrient storage and flow for terrestrial ecosystems. The amount of nutrients in each compartment is indicated by the size of the circle and the flow rates are indicated by the size of the arrows. B is biomass, L is litter, S is soil.

Climax Community

Ecological succession usually stops when a stable ecosystem develops with a group of organisms called the climax community

Ecological succession

series of changes to an ecosystem, caused by complex interactions between the community of living organisms and the abiotic environment. Primary succession starts in an area where living organisms have not previously existed, for example a new island, created by volcanic activity

Characteristics Of Ecosystem Increased during primary succession

species diversity +

\
plant density +

\
organic matter +

\
soil depth +

\
water holding capacity +

\
soil erosion -

\
nutrient cycling +

environmental disturbance

Communities sometimes change from those predicted by climographs to other communities as a result of environmental disturbance.

\
e.g flood, fire, storm

Endemic Species

Species that naturally occurs in the area

Alien Species

organism that humans have introduced to an area where it doesn’t naturally occur

Starlings

Example Of Alien species that compete with endemic species for nest spots and food.

Cane Toad

Example Of Alien species that releases toxins threatening local endemic population. Reproduce quickly, (produce 30000 eggs).

\

biomagnification

pollutants absorbed into living organisms - accumulates in high concentration as it cannot be excreted

\
Increases across trophic levels due to biomagnification.

Biological Control

use of predator, parasite or pathogen to reduce/eliminate pest.

Plastic Pollution In Oceans

Plastics are dumbed at sea and are resistant to decomposition. Macroplastics (large plastics) and microplastics (small plastics) degrade into debris and accumulate in marine environments called gyres.

Richness

The number of different species present (a type of biogeographic factor

Evenness

how close in numbers, the different species are. (a type of biogeographic factor)

\

Biogeographic factors

the number of species that live in an area is greatly affected by

edge effect

certain species avoids living close to edge of forest, thus those species are absent from forest which are fragmented.

In situ conservation

conserving a species in its own habitat. i.e natural reserves/national parks)

Ex Situ

threatened population transfered to captivity in zoo’s or wild refuges due to loss or destruction of natural habitat.

Indicator Species

Used to measure tolerance of specific environmental condictions

Lichen

(example of indicator species)

\
Used to assess tolerance of concentration of sulfur dioxide pollutant in desired area.

\

Biotic Index

\[(No. Of Indicator Species)(Pollution Tolerance Rating)\] ÷ (total number of organisms)

\
(Note: The higher the biotic index, the less polluted)

Capture-Mark-Release-Recapture (CMRR)

1)Capture as many individuals as possible in the area of a population and discretely mark them

2)Release the marked individuals to settle back into habitat.

3)Recapture all individuals an count how many are marked and unmarked.

Lincoln Index (estimated population size)

\[(Initial Caught And Marked)(Total Caught In Second Capture)\] ÷(number of marked recaptured)

Substainable fishing practices

The maximum sustainable yield is the largestamount that can be harvested without a decline in stocks. It is essential to know the age profle, reproductive status and size ofthe population. If the population drops too low for efective breeding, there must be a ban on fishing. Suficient larger fish that are mature enough to reproduce must be left for the population to replenish itself as least as fast as fish are caught.

Natality (Population Growth Factor)

Offspring produced and added to the population

Mortality (Population Growth Factor)

Individuals die and are lost from the population

immigration (Population Growth Factor)

individuals move into the area from elsewhere

emigration

individuals move from the area to live elsewhere

Formula For Population Change

(Natality + Immigration) - (Mortality + Emigration)

Sigmoid Graph

An S shaped population growth curve.

1. Exponential Phase

In an ideal environment, the population follows exponential growth.

\
Natality Rate > Mortality Rate

Immigration > Emigration

2. Transitional Phase

Population growth slows as the carrying capacity of the environment is reached

\
Natality Rate Decreases

Immigration Decreases

3. Plateau Phase

Population Limited By Food, Predators, Disease and Parasites

\
Natality Rate = Mortality Rate

Immigration < Emigration

\

Nitrogen Fixation

Conversion of N2 in atmosphere to Ammonia (NH3) using ATP

\
\

Nitrification

Converts ammonia to nitrate

\

Denitrification

Conversion of nitrate back to nitrogen bu denitrifying bacteria. (Only occurs In soil In absence of oxygen)

Waterlogged Soils

Oxygen In Waterlogged soils is used up quickly, preventing production of nitrate, resulting in nitrate deficiency.

Eutrophic

Nutrient concentrations that are dangerously high.

Algal Bloom

Eutrophication causes algae to multiply excessively, resulting in an algal bloom.

\
\-lower algae deprived of light and die.

\-bacteria decompose dead algae leading to increased biological oxygen demand

biological oxygen demand

\

Higher the biological oxygen demand in water, the more polluted and the more organisms die.

limiting factors

prevents eutrophication

bottom up control (limiting factor)

(shortage of nutrients)

Top-down control (limiting factor)

(control by means of predators or parasites)

parrotfish

example of top-down limiting factor that controls algae population as a predator that eats algae via herbivory.

The Nitrogen Cycle (See diagram)

\

1. Nitrogen fixation: Conversion of atmospheric nitrogen into ammonia by bacteria
2. Nitrification: Ammonia is converted into nitrite and then nitrate by bacteria
3. Assimilation: Plants absorb nitrate or ammonium to make amino acids and other organic compounds
4. Ammonification: Decomposers break down organic compounds into ammonium
5. Denitrification: Conversion of nitrates back to atmospheric nitrogen by bacteria in anaerobic conditions.

\

culling

control of wild animal populations through selective slaughter (biotic factor)