BIO3 - Exam revision

Estimating total populations - formula

Total number = (number counted x total area)/ area sampled

Estimating population density - formula

Density = Total number counted/Area sampled
(no. area-n)

Quadrat sampling

is a method by which organisms in a certain proportion (sample) of the habitat are counted directly.

Calculating Abundance (total number) - formula

Calculating Estimated Average Density - formula

What are the three types of transect sampling?

- Point sampling
- Continuous belt transect
- Interrupted belt transect

Zonation

changes in community composition along
an environmental gradient.

Pros/Cons of transect sampling
(Recognition)

 Advantages
Good for showing zonation
 Disadvantages
Low density organisms may not be sampled
Larger organisms have a greater chance of
being sampled by a line transect

Capture Recapture method

 Used for counting organisms that move, or
for monitoring populations over time.
 A sample of organisms are captured,
marked and released. At a later point in
time, another sample is captured, and the
number of marked organisms in the
second sample is counted and recorded.

Capture recapture cons (Recognitions)

Accuracy depends on capturing a fairly large proportion of the population. ...
Many study populations are not geographically closed because only a part of a population's range is included in the study area.

Lincoln index

Total population = (# of marked in 1st sample X total # in 2nd sample)/# of marked in 2nd sample

or

N = (n1 x n2)/n3

Indirect sampling - Advantages and disadvantage
(Recognition

 Trails, droppings, burrows etc
 Camera traps
 Advantages
 Good for individuals that are difficult to physically
count
 Doesn’t harm organism
 Disadvantages
 You have to know a relatively large amount of
background information. E.g. how many individuals
per burrow
 Less accurate

Species richness

is a measure of the number
of different species found in a sample.

Species evenness

a measure of the relative
abundance of the different species making
up the richness of an area.

Species diversity

takes into account both the numbers
of species present and the dominance or
evenness of species in relation to one another.

Diversity Index - Simpson's diversity index - formula

A diversity index is a measure of the number
of different organisms in an ecosystem.

DI = (N(N-1))/(Σn(n-1))

DI=Diversity Index
N=total number of individuals from all species
n=number of individuals of each species

Chi squared analysis - formula

 X2 = is the Chi value
 ∑ = sum
 o = observed value
 e = expected value

Degrees of freedom - formula

DF = (Column - 1)(Row - 1)

Testing for independence/ Association - method

1) Determine null hypothesis
2) Enter observed results in a contingency table
3) Calculate the expected values
 For each category divide the row total by the
grand total and multiply by the column total.
4) Calculate Chi-value
5) Calculate the degrees of freedom and look
up the chi-value on a probability table, and accept
or reject the null hypothesis.

Population

the number of inhabitants in a given place

Community

All populations of different species living in an
area

Ecosystem

All of the biotic (living) and abiotic (non-living)
factors in an area.

Population distribution + Abundance

Density - number/area or number/volume
Distribution - location within area
Size/abundance - total number of
individuals

Name and describe the 3 types of distribution

[Random distribution]
 The spacing between individuals is irregular. The
presence of one individual does not directly affect the
location of any other individual. Commonly seen in
plants.

[Clumped distribution]
 Individuals are grouped together in certain areas, often
around a resource. e.g. a waterhole.
 Also when living in large groups is beneficial.

[Uniform distribution] individuals are evenly and
regularly spaced in an area.

Explain what population density tells us about the species

 Low density - only a few individuals per
unit area. Often highly territorial, solitary
mammalian species such as tigers.
 High density - individuals are crowded
together, many individuals per unit area.
Often colonial organisms, such as corals
or insects.

Population growth - formula

PG = (births – deaths) + (immigration – emigration)
 Birth rate= births per 1000 per year
 Death rate= deaths per 1000 per year
 Immigration= movement of individuals into the
population
 Emigration= movement of individuals out of the
population

Population composition

- Sex Ratios: Ratio between male and female
- Population fertility: Reproductive capacity
- Age structure: Number of organisms of different ages

Malthus’s Theory of Population Growth
(recognition)

 Populations increase exponentially, while food
production increases arithmetically.
 Hence population growth easily outstrips
resource production.
 Thus, populations increase quickly, until
competition for resources occur and the
carrying capacity is reached.

Exponential growth

J- Shaped curve of population growth

Logistic growth

S - Shaped curve of population growth

Carrying capacity (K)

The carrying capacity is the maximum
number of individuals an area can
support on a sustained basis given the
prevailing resources.

r and K selection

Many organisms fall under two main
reproductive strategies, r strategists or K
strategists.

- r strategists often follow a J-shaped
growth curve
- K strategists often follow a S-shaped
growth curve

Density independent factors

Abiotic factors:
- Rainfall
- Temperature
- Salinity
- Terrain
- Natural disasters etc

Density dependent factors

Biotic factors:
Food supply
Parasites
Disease
Competition
Predation

Nutrient cycling

a system where energy and matter are transferred between living organisms and non-living parts of the environment.

Role of each in nutrient cycling:
- Bacteria
- Fungi
- Plants
- Animals

- Bacteria: Act as decomposers and convert nutrients into forms that can be used by plants and animals
- Fungi: Saprophytes and decompose nutrients into forms accessible by plants and animals
- Plants: Absorb nutrients from the soil to make them available for animals and contribute their decaying matter to solids. Additionally, plants can also consume nutrients via cellular respiration.
- Animals: Consume and break down materials from plants, bacteria and fungi and return the nutrients after they die

The carbon cycle

cycling of carbon in an ecosystem

Methanogens

 Methanogenic bacteria (archaeans) release
carbon in the form of methane (CH4).
 This process usually occurs in anaerobic conditions
such as swamps and bogs and can cause dead
organic matter to not be fully decomposed by
saprotrophs.
 It can also occur in the digestive bacteria of
ruminant mammals.
 Methane is usually taken up by methane sinks such
as soil or can be oxidised to CO2 in the
atmosphere

Sink

Storage unit for large quantities of carbon ie the atmosphere/ the ocean

What affects the speed of nutrient cycling?

- Environment (ie forest disturbances by rainfall/ weather patterns)
- Ecosystem - Competition for resources, community interactions etc

Name the processes that release carbon into the atmosphere

- Combustion
- Oxidation
- Respiration
- Decomposition

Name the processes that absorb carbon into sinks

- Photosynthesis
- Fossilisation
- Sedimentation
- Dissolving (of CO2 into the ocean)

Describe the biological origin of:
- Coal
- Oil and natural gas
- Limestone
- Peat

Due to acidic and anaerobic conditions in some wetlands/swamps, saprotrophs are unable to fully break down organic matter so overtime it forms thick deposits called peat. Layers on top of the peat plus time, pressure and heat and it forms coal.
Silt, sediment and organic matter can be deposited in shallow seas but again, the anaerobic conditions can prevent the organic matter from being fully decomposed.
The silt converts to rock and organic matter forms coal, oil or gas deposits

Carbon flux

describe the rate of exchange
of carbon between the various carbon sinks /
reservoirs.

How is carbon stored? (name 4 sinks)

Atmosphere: Atmosphere - Carbon dioxide
Hydrosphere: Ocean - Carbonate and bicarbonate
Lithosphere: earths crust - Rocks and limestone
Biosphere: organisms - methane or hydrocarbons

The nitrogen cycle

Nitrogen fixation

Nitrification

 Nitrification is the conversion of ammonia to
nitrate.
 Two types of soil bacteria are involved:
 Nitrosomonas convert ammonia to nitrite (NO2-)
 Nitrobacter convert nitrite to nitrate (NO3)

Denitrification

 Denitrification is the conversion of nitrate into
nitrogen.
 This process only occurs in the absence of
oxygen in the soil by denitrifying bacteria
(Pseudomonas).

Ammonification

The nitrogen cycle - processes involved

4 Groups of bacteria involved in the nitrogen cycle and their function

Rhizobium - nitrogen fixation, fix nitrogen (N2) as ammonium (NH4)
Nitrosomonas - nitrification, convert ammonium (NH4) to nitrite (NO2-)
Nitrobacter - nitrification, convert nitrite (NO2-) to nitrate (NO3-)
Pseudomonas - denitrification, convert nitrate (NO3-) back to nitrogen (N2)

Sources of water pollution

- sediment
- sewage
- infectious particles
- organic compounds (oil spills)
- thermal changes
- radioactive pollution
- inorganic chemicals
- Plastic waste
- inorganic plant nutrients

Sources of air pollution

Forest fires, volcanic activity, burning of fossil fuels, industry and vehicles all can produce air pollution.
 In the presence of sunlight, the mixture of pollutants from industry and vehicles reacts to form smog (e.g. ozone, nitric acid, formaldehyde).

Eutrophication

Eutrophication is the enrichment of an ecosystem (typically aquatic) with chemical nutrients (nitrates, phosphates, etc.)
The nutrients can be introduced via leaching from soil by rainfall or released as part of sewage

Indicator species - name examples

A species whose presence, absence or abundance
reflects a specific environmental condition, habitat or
community.

Air pollution:
- Clean air: lichen and black spot fungus (roses go brr)

Water pollution:
clean water
- mussels
- mayfly

low pollution - shrimp
high pollution - water louse
very high - sludge worms and bloodworm

EPT% +

Percent EPT is short for the total number of Ephemeroptera (mayflies), Plecoptera (stoneflies), and Trichoptera (caddisflies). Many species within these three groups are sensitive to changes in water quality.

Biomagnification

Biomagnification refers to a pollutants ability to increase in concentration as it moves from one trophic level to the next. It involves an increase in concentration from one link in a food chain to another due to
the relative amount each organism in the chain consumes.

Bioaccumulation

Bioaccumulation refers to how pollutants enter
a food chain or food web. It involves an increase in concentration of a pollutant from the environment to the tissues of an organism. Smaller, simpler organisms towards the bottom of a food chain will often absorb these pollutants more easily.

Ecological disturbance

Ecosystems change from disturbance
 Land clearing or conversion of ecosystems for urban
development, agriculture/farming/plantations, or
industry (mining, manufacturing etc)
 Dam creation (for water catchment or electricity
generation)
 The introduction of introduced invasive species

HIPPO

H - Habitat loss

I - Invasive species

P - Pollution

P - Population

O - Overuse

Alien / invasive species

An alien species is an organism introduced
either intentionally or accidentally by humans
to an area where it does not usually occur.

Endemic species

An endemic species naturally occurs in a
particular habitat or ecosystem.

Island geography and Nature Reserves - How do we minimise damage to an ecosystem?

Large habitats are better
 More resources, niches, nesting sites etc
 Some migration can occur
 Greater biodiversity

Corridor effect
 Joining regions allows for more migration, foraging, dispersal etc

Edge effect
 Boundaries are not “walls” and there is habitat disturbance
that extends into the area, particularly in forests.
 If the forest is more fragmented and has more edges, more
of the area will be disturbed.

In situ conservation

In situ conservation involve the species
remaining in their natural habitat. Often active
management is still necessary such as:
 Control of alien/invasive species
 Reintroduction of natives species
 Limiting predators
 Feeding programs
 Limiting access

Ex situ conservation

Ex situ conservation involve the removal of species
from their natural habitat.
 This can include botanic gardens, captive breeding
programs and zoos.

Greenhouse gas

Gases which contribute to the greenhouse
- Water vapour
- CO2
- Methane
- Fluorinated gases
- Nitrous Oxides NO2

Greenhouse effect

The greenhouse effect is the way in which heat is trapped close to Earth's surface by “greenhouse gases.”

Albedo

Why would you use a biotic index regarding pollution?

To compare the relative frequency of indicator species and provide an overall environmental assessment of an ecosystem.