2. Read the descriptions below and choose the correct keyword being described.
1. All the organisms of a single species living in a habitat.
2. The populations of different species living in a habitat.
3. The non-living factors of an environment.
4. The living factors of an environment.
5. The interaction between the living organisms and the different factors
of the environment.
Starter Task Answers
Population
Community
Abiotic
Biotic
Ecosystem
Abiotic factors can include the following: moisture, light, temperature,
CO2, wind, O2 or soil pH.
Biotic factors can include the following: predators, competition,
pathogens, availability of food.
abiotic biotic community ecosystem population
3. Key Terms
Species consisting of similar individuals capable of exchanging
genes or interbreeding to produce fertile offspring.
All the organisms of a species living together in a habitat are
called a population.
The different populations which live together in a habitat are
called a community.
The living things and their interactions with the environment
they live in is called an ecosystem.
An individual, living thing is called an organism.
5. Abiotic factors affecting the abundance &
distribution of organisms
Light
Some plants have evolved for optimum growth in bright
sunlight. An example of this is a cactus houseplant. Cacti
originally come from deserts where they grow in bright
sunlight. Other plants have evolved to grow in shade.
Many orchids, which are also kept as houseplants, grow
on trees in the rainforest and have evolved for optimum
growth in darker conditions. If you were to put an orchid
on a bright windowsill and a cactus in a dark corner of
your room neither plant would grow well.
6. Abiotic factors affecting the abundance &
distribution of organisms
Temperature
Both animals and plants have evolved to grow healthily
at their optimum temperatures. If you planted either
your cactus or orchid houseplants outside in cold
temperatures, they would die. Similarly, animals that
have evolved to live at the North Pole, such as the polar
bear
, could not survive in warmer conditions.
7. Abiotic factors affecting the abundance &
distribution of organisms
Moisture levels
More people kill houseplants by overwatering than by
under-watering them. Many plants cannot survive in
waterlogged soils. Their roots are unable to respire, they
rot and the plant dies. Other plants, such as pitcher
plants, grow best in bogs where the moisture levels are
high. Soil moisture meters can accurately determine how
wet an area is.
8. Abiotic factors affecting the abundance &
distribution of organisms
Soil pH content
The pH of soils can have a huge effect on the plants that
are able to grow in them. Some plants, like azaleas, grow
best in acidic soils and will quickly die if planted in
alkaline soils. Others, like clematis, prefer alkaline soils.
Some, like the hydrangea, can grow in both. These plants
are unusual in that their flower colour changes in
different soils. Just like universal indicator paper,
hydrangea flowers are pink in acidic soils and blue in
alkaline soils.
9.
10. Abiotic factors affecting the abundance &
distribution of organisms
Soil mineral content/Substrate
Many plants require high levels of soil minerals to grow
well. An example of this is magnesium, which is required
to produce chlorophyll. Plants with unnaturally yellow
leaves may have a magnesium deficiency. Carnivorous
plants, such as pitcher plants, have evolved to catch
insects to supplement the low levels of minerals found in
the soils in which they grow.
11.
12. Abiotic factors affecting the abundance &
distribution of organisms
Carbon dioxide
Carbon dioxide is a reactant in photosynthesis which
means plants need it to survive. Areas with higher levels
of carbon dioxide are more likely to have healthy plants
growing. Farmers often release carbon dioxide within
their greenhouses to maximize their crop yield.
Woodlands often have higher carbon dioxide levels than
open grassland, so many plants living in open areas have
evolved mechanisms to overcome a shortage of carbon
dioxide.
13. Abiotic factors affecting the abundance &
distribution of organisms
Oxygen levels for aquatic animals
Oxygen from the air and oxygen produced by aquatic
plants dissolves in water
. Without this, aquatic animals
would suffocate and die. Healthy lakes and rivers have
high levels of oxygen, and polluted waters often have low
levels of oxygen. This pollution means that only
certain species can survive there such as sludgeworms.
These are bioindicator species because their presence or
absence informs us about the condition of the habitat.
14. Abiotic factors affecting the abundance &
distribution of organisms
Wind
The strength of the wind and its direction has a huge
impact on where organisms are found within ecosystems.
Many organisms prefer more sheltered locations. Plant
seeds are more likely to settle and germinate there, and
animals which depend upon these are more likely to live
close to where they grow. The strength of the wind can
also affect the growth of individual organisms.
15. Two types of interactions between living things in their
environments are competition and interdependence.
Competition vs Interdependence
Interdependence
All organisms in an ecosystem depend upon each
other
. If the population of one organism rises or falls,
then this can affect the rest of the ecosystem.
16. Competition vs Interdependence
A simple food chain is:
If the foxes in the food chain above were killed, the
population of rabbits would increase because they are no
longer prey to the foxes. As a result the amount of grass
would decrease because the increased population of rabbits
would be eating it.
Often very small changes to ecosystems have large
consequences, which can be difficult to predict. This means
that all the organisms in an ecosystem are dependent upon
each other
. We call this interdependence.
17.
18. Competition vs Interdependence
Competition is the struggle between two organisms for
the same resources within an environment. Resources
are components of the environment that are required
for survival and reproduction such as food, water
,
shelter, light, territory, and substrate. Members of the
same species may also compete for mates.
19. Types of Competition
1. Intraspecific Competition – The competition
between organisms of the same species for a
common resource.
20. Types of Competition
2. Interspecific Competition – The competition which
occurs between organisms of different species for a
common resource.
21. Interdependence is the interaction between two or
more organisms where it is mutually beneficial.
Competition is the negative interaction between
two or more organisms which require the same
limited resource.
Remember, plant species can be interdependent.
They can also compete for resources such as light,
moisture and nutrients in the soil.
22. Read the information given about the four different situations. Use the
information to complete the table below.
How Factors Affect Populations
Description of
Scenario
Affecting
Factor
Abiotic or
Biotic?
Describe how species populations are
affected – increase or decrease
population? Explain why.
red and grey squirrels
cane toad introduction
to Australia
milkweed plant and
monarch butterflies
Chalara dieback of ash
23. Red and grey squirrels live in the same habitat and eat the same food.
Grey squirrels outcompete the red squirrels.
Red and Grey Squirrels
24. In 1935, cane toads were introduced to Australia as a biological pest control
of the grey-backed cane beetle.
The toads have no natural predators in Australia.
Cane Toads
25. The milkweed plant is pollinated by insects such as the monarch
butterfly. The monarch butterfly will only lay its eggs on milkweed
leaves. However, people often consider milkweed as an invasive weed
and use weed killers to remove them in their gardens.
Milkweed and Monarch Butterflies
26. In 2012, cases of Chalara dieback of
ash were discovered on ash trees
being imported from Europe. Later in
the year, it was discovered that ash
trees in established British woodland
showed signs of the disease.
Chalara Dieback of Ash
