N5- Unit 3
Biodiversity and the distribution of life
1- Species
Group of organisms which can interbreed and
produce fertile offspring.
2- Habitat
The place where an animal or a plant lives.
3- Population
4- Community
5- Ecosystem
6-What is meant by
biodiversity?
7-What can decrease or
increase biodiversity?
8- Biotic factors
9-Describe how grazing
pressure affects biodiversity.
10- Abiotic factors
11-Describe how pH can affect
biodiversity in lochs?
12-Describe how temperature
affects biodiversity in lochs?
Total number of organisms of the same species
living in the same area.
All the populations from different species living in
the same area.
All the organisms (i.e. the community) living in a
particular habitat and the non-living components with
which the organisms interact (i.e. abiotic factors)
The total variety of organisms living on Earth.
- biotic factors
- abiotic factors
- human activities (pollution air/water, habitat
destruction. deforestation, overfishing, overhunting.
Living influences on an ecosystem:
- Competition for resources
- food availability
- Number of predators
- Disease
- grazing
Low grazing pressure: Vigorous plants become
dominant: low biodiversity
Medium gazing pressure: greater biodiversity as the
vigorous plants are kept under control which give
opportunity for others to grow
High grazing pressure: low biodiversity as no plants
have the opportunity to grow.
Non-living influence on an ecosystem:
- air/water/soil temperature
- soil/water pH
- air/soil moisture
- light intensity
Only few species can tolerate a wide range in pHs.
Many species will not survive if water pH changes
slightly. Therefore changes in pH can result into
reduced biodiversity.
Warmer waters contain less dissolved oxygen. Many
fish cannot tolerate a drop in oxygen levels.
Therefore, water temperature and influence on
oxygen concentration has an effect on biodiversity.
13-What is the name given to
all the plants in an ecosystem?
14-What is the name given to
all the animals in an
ecosystem?
15-Biome
16-Niche
Flora.
Fauna.
Various regions of our planet as distinguished by
their climate, flora & fauna.
The role that an organism plays within a community.
This includes the use it makes of resources in its
ecosystem, including light, temperature and
nutrients availability and its interactions with other
organisms in the community including competition,
parasitism and predation.
Energy in ecosystems
1-Describe what is meant by the
words producer and consumer.
2-Herbivore
3-Carnivore
4-Omnivore
5-What is lost at every step of a
food chain?
6-How much of it is lost and how?
7-Explain what is meant by the
terms pyramid of numbers (1) and
pyramid of biomass (2) (and
pyramid of energy(3))
8-Investigate irregular pyramids
of numbers
9-Why does competition occur in
ecosystems?
10-What is the name given to
competition between organisms of
the same species?
11-What is the name given to
competition between organisms of
different species?
12-Which of these 2 types of
competition is the most intense?
Producer : makes its own food from the energy
of sunlight (e.g. green plants).
Consumer: needs to eat other organisms to feed
itself (e.g. all animals)
Animal which eats only plants.
Animal which eats only meat.
Animal which eats both plants and meat.
Energy
90% of energy is lost as heat energy, movement
and undigested materials, 10% of energy is used
for growth.
(1) shows the number of organisms at each level
of a food chain.
(2) shows the total mass of organisms at each
level of the food chain.
(3) shows the total energy at each level of the
food chain
Check jotter/book.
When organisms require similar resources which
are in short supply. Example of resources
include: need for food, light and water.
Intraspecific
Interspecific
Intraspecific.
Nitrogen in ecosystems
1-Where does the nitrogen used
to produce plant proteins come
from?
2-Where does the nitrogen used
to produce animal proteins come
from?
3-Role of nitrifying bacteria?
4-Role of denitrifying bacteria?
5-Role of root nodule bacteria?
6-Role of free-living nitrogenfixing soil bacteria?
7-Role of decomposers?
From nitrates
By animals eating plants and/or other animals.
Nitrification step 1: convert ammonium compound
into nitrite.
Nitrification step 2: convert nitrite into nitrate.
Use directly the nitrate from soil and release
nitrogen gas as a waste. This removes useful
nitrogenous compounds from the soil.
Nitrogen fixation inside root nodules to produce
a form of nitrogen compound usable by the plant.
Nitrogen fixation of bacteria which can use
atmospheric nitrogen directly to produce
nitrates.
Bacteria & fungi which convert protein and
nitrogen wastes to ammonium compounds.
By supplying them with fertilisers which contain
nitrates.
8-How do human insure that plants
have access to enough nitrates to
grow well?
Sampling techniques of biotic and abiotic factors
1-Biotic factor: estimate
Quadrats:
population of plants.
Technique: square-shaped frame throw
Techniques, source of error and
randomly at various places. The number of plants
way to minimize it.
of each type is counted → the total number of
each species can be calculated.
Source of error and way to minimize it
1- If too few quadrats have been counted, the
number of plants may not be representative as
some species grow in clusters.
→ use large number of quadrats for study
2- Some plants may be spreading on either side
of the frame. → overestimation (counting them
all) or underestimation numbers (not counting
them).
→ use a rule: e.g. plants going across the top and
bottom sides are counted and these going across
the right and left sides are not.
2-Biotic factor: sampling of
invertebrates living on a
bush/hedge.
Techniques, source of error and
way to minimize it.
3-Biotic factor: sampling of
crawling invertebrates
Techniques, source of error and
way to minimize it.
4-Biotic factor: sampling of
invertebrates living on a river bed
Techniques, source of error and
way to minimize it.
5-Abiotic factor: light intensity.
Instrument used, source of error
and way to minimize it.
6-Abiotic factor: air/soil/water
temperature.
Instrument used, source of error
and way to minimize it.
7-Abiotic factor: soil moisture
8-Abiotic factor: water/soil pH
9-How to study the effect of an
abiotic factor on the distribution
of a species (i.e. where it found
growing).
10-State the effect an abiotic
factor has on the distribution of
organism
Tree-beating
Technique: the branches of a tree are beaten
with a stick and a tray is used to collect the
falling small animals
Source of error and way to minimize it
Animals may fall beside the tray
→ use large tray with raised edges, empty the
tray regularly using a large plastic bag or use a
potter to isolate animals.
Pitfall trap
Technique: a beaker is inserted into the soil so
that the rim is leveled with surrounding ground.
Source of error and way to minimize it
Some trapped animals might eat other smaller
animals.
→ add salty water in the trap to kill the animals
→ Kick sampling: use a net and kick the river bed
directly upstream of the net.
→ kick right next to the net to avoid losing
organisms transported by the current.
→ transport the sample fast to a bucket to avoid
loosing small organisms.
→ Use a light meter
→ avoid casting a shadow on the light meter
→ Use a digital thermometer
→ wait until temperature readings stop changing
→ use a soil moisture probe
→ make sure that probe is inserted in soil to the
same depth + clean/dry the probe between
measurements.
→ use a pH meter.
→ make sure that probe is cleaned/dried
between measurements.
Make a transect: tie a string between two points
to obtain sampling sites (e.g. every meter) along
the area where the abiotic factor changes in
intensity.
Combination of abiotic factors determines which
plants grow in any one place (e.g. exposure to
wind, moisture levels etc…). Types of plants
determine type of animal.
Adaptation, natural selection and the evolution of species
1-What are mutations?
A mutation is a random change to genetic
material.
Mutations are spontaneous and are the only
source of new alleles.
2-What types of mutations exist? Mutations may be neutral, confer an
advantage or a disadvantage.
3-Give examples of environmental
Environmental factors, such as radiation (UV,
factors which increase the rate of Gamma, X rays), high temperatures and some
mutations.
chemicals (e.g. mustard gas, colchicine), can the
increase rate of mutation
4-Describe the part played by
- mutations are random changes to the genetic
mutations and natural selection in
material
the evolution of a species
- advantageous mutations give a selective
advantage which allows survival
- favorable mutations are passed on to offspring
5-Why are alleles produced by
New alleles produced by mutation allow
mutation important to a
plants and animals to adapt to their
populations?
environment.
Variation within a population makes it possible
for a population to evolve over time in response
to changing environmental conditions.
6-What is meant by “adaptation”? An adaptation is an inherited characteristic
that makes an organism well suited to survival in
its environment/niche.
7-Different types of adaptation?
Structural (e.g. change of beak shape)
Behavioural (e.g. tool use, swarming behavior)
8-What are the principles of
1- There is genetic variation in a population
natural selection?
2- There is more offspring than the
environment can sustain resulting in
selection pressures.
3- Only the best adapted individuals survive
to reproduce and pass on their genes
which confer a selective advantage.
9-What is the name given to the
Speciation.
evolution of a new species?
10-What are the different steps
1- Isolation: a population becomes isolated by
resulting in speciation?
an isolation barrier.
2- Mutations occur in each sub-population.
3- Natural selection selects for different
mutations in each group, due to different
selection pressures.
4- Each sub-population evolves until they
become so genetically different they are two
different species.
11-Examples of isolation barriers
Human impact on environment
1-Why do we try to increase food
yield?
2-What sort of chemicals are
spread onto crops and why?
3-Give three examples of how
food yield is increased.
4-Explain GM crops.
5-Explain how GM crops can help
to reduce the need for pesticides
with pros/cons.
6-Explain how GM crops can help
to reduce the need for fertilisers
with pros/cons
7-Explain monoculture and
intensive farming and its
pros&cons
- geographical: mountain/desert/sea
- ecological: pH, temperature, moisture
- reproductive: non-matching mating seasons.
Because the human population increases.
- Pesticides: to kill pests, i.e. usually
invertebrates eating crops.
- Herbicides: to kill weeds which compete with
crops for light/ water/ nutrients and reduce
yield/hectare
- Fertilisers: to provide mineral elements needed
for plant growth which otherwise would be
rapidly depleted from soil.
- GM crops
- Monoculture & Intensive farming
= when a useful gene is inserted into a crop plant
increasing its yield/hectare.
The useful gene gives resistance to a pest which
increases the yield/hectare as less of the crop is
lost to pests.
Pros: less/no pesticides sprayed on crops:
beneficial insects survive
Cons: pest evolves resistance/ resistance may be
transmitted to local species creating more
problems
The useful gene helps a plant taking up nitrogen
more efficiently thereby increasing the
yield/hectare.
Pros: No need/lesser need for fertilisers which
cost money and leach into waterways.
Cons: Risk of gene transfer to local weed which
can then become more difficult to control.
Intensive farming: when farmers use
monoculture, huge quantities of fertilisers and
pesticides/herbicides to increase yield per
hectare and rear animals in battery-farms
Intensive farming:
Pros= increased yields to sustain the growth of
the human population
Cons:
- needs lots of fertiliser
- biodiversity greatly reduced
- extensive use of antibiotics in animals leading
to antibiotic-resistant strains of bacteria.
8-Problems linked to heavy use of
fertilisers beside rivers and loch
9-What are indicator species?
10-Examples of indicator species
for air quality
11-What is bioaccumulation?
12-What is biological control?
13-Pros and Cons of biological
control
Good luck for the exam!!!
Monoculture= extensive cultivation of one
genetically identical type of crop plant.
Pros: makes farming more efficient as the same
method/material is used throughout.
Cons:
- needs lots of fertiliser
- biodiversity greatly reduced
- if a new disease successfully attack the crop, it
easily spreads.
- Fertilisers can leach into rivers and loch.
- It promotes growth of algae (algae bloom)
- Algae rots and decomposed by aerobic
bacteria.
- water desoxygenated
Kind of organism that by their presence or
absence give levels of pollution.
Low levels of pollution by sulphur dioxide (from
burning fossil fuels):
Great diversity and hairy/leafy lichens.
High levels of pollution by sulphur dioxide:
Only crusty lichens found.
Pesticides sprayed onto crops can accumulate in
the bodies of organism over time. As they are
passed along food chains, toxicity increases and
can reach lethal levels.
An alternative to the use of pesticides.
The deliberate introduction of a natural
predator to a pest to reduce its numbers.
E.g. – Use of a virus (myxomatosis) to control
rabbits.
- Use of ladybirds to kill aphids.
Pros: less pesticides are sprayed on the crop
which is better for the biodiversity of the local
ecosystem.
Cons: the predator can start to feed on other
organisms than the pest and create problems in
the local ecosystem.