Section 1.4 Ecology (Higher Level)
Population
Ecology
Section 1.4 Ecology (Higher Level)
H.1.4.11 ECOLOGICAL
RELATIONSHIP
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Factors that control populations.
Definition of “competition”
Examples:
contest competition – an active physical confrontation between two organisms
which allows one to win the resource
scramble competition – each organism tries to acquire as much of the resource as
possible.
Relate competition to size of population.
Outline one adaptive technique of an organism to survive competition.
Definition of “predation”.
Examine any three adaptive techniques of (a) predators and (b) prey. Give one
simple example of a predator/prey relationship
to illustrate population control.
Definition of “parasitism” with example.
Definition of “symbiosis” with example.
Section 1.4 Ecology (Higher Level)
Ecological Pyramids
• Pyramids of numbers represent feeding
stages in a food chain
Section 1.4 Ecology (Higher Level)
Normal shape looks like a pyramid!
Usually as you go up the pyramid:
•The number of individual organisms decrease
•The size of the individual organisms increase
Section 1.4 Ecology (Higher Level)
Limitations of Pyramids of Numbers
• It doesn’t take account the size of each organism.
A grass plant and a
tree would each
count as one
organism, even
though the oak tree
can feed lots more
consumers!
Section 1.4 Ecology (Higher Level)
Inverted pyramid of numbers
• If the producer is very large the pyramid
will have an inverted shape
Hawk
Blackbird
Ladybird
Greenfly
Oak Tree
Section 1.4 Ecology (Higher Level)
Population
Ecology
Section 1.4 Ecology (Higher Level)
What you should learn about
today..
• What a population is
• What competition is and the difference
between the two types
• What adaptations are and examples
• Definitions and examples of parasitism
• Definitions and examples of symbiosis
Section 1.4 Ecology (Higher Level)
Population ecology
A population is all the members of a species living in an area.
The population of Blue Whales on earth is 1,300 to 2,000 
Section 1.4 Ecology (Higher Level)
Section 1.4 Ecology (Higher Level)
Competition
• Def Competition is when organisms struggle
for a resource that is in short supply
Section 1.4 Ecology (Higher Level)
Contest competition
• Contest competition is when there is an active physical
confrontation between two organisms which allows one to win
the resource.
Section 1.4 Ecology (Higher Level)
Scramble competition
• In scramble competition the organisms share
the resource - each will try to get as much as
possible for themselves.
Aphids display scramble
competition as they
compete with each other
for food
Section 1.4 Ecology (Higher Level)
Adaption
Organisms adapt to reduce competition.
The white butterfly adapts to its environment by having special
eating habits. As a caterpillar it feeds on cabbage, but as an adult
butterfly it feeds on nectar. This reduces competition for food
between young and old members of the population!
Section 1.4 Ecology (Higher Level)
Predation
• Def Predation is when one organism
catches and kills another organism for
food.
Ladybird (the predator)
kills and eats the aphid
(prey)
Prey and predator relationships can be used to control population sizes.
Ladybirds can be introduced into an area to reduce numbers of aphids
Section 1.4 Ecology (Higher Level)
Adaptations for feeding
relationships
• The skills of a predator are based around
finding, catching and killing prey
• The skills of prey species are based
around awareness and avoidance of
predators.
• Herbivores need the skills to find and eat
their food.
Section 1.4 Ecology (Higher Level)
Adaptations of Predators
•1. ladybirds have strong mouth
parts to chew aphids
• 2. Cheetahs are camouflaged to
help them to hide from their prey.
• 3. Wolves hunt in packs to catch
and kill their prey
Section 1.4 Ecology (Higher Level)
Can you spot the second cheetah?
Section 1.4 Ecology (Higher Level)
Adaptations of Prey
• 1)Camoflage -The baby harp
seal's white coat makes it hard
for predators to spot the young
seal on the ice.
2) Some plants have thorns to
discourage herbivore predators
from eating them
3) The yellow dart frogs excrete
poison to discourage predators from
eating them
Section 1.4 Ecology (Higher Level)
Check your learning...
• What a population is
• What competition is and the difference
between the two types
• What adaptations are and examples
• How prey are adapted to survive
• How predators are adapted to survive
Section 1.4 Ecology (Higher Level)
Adaptations of caterpillars
activity
• http://teacher.scholastic.com/activities/expl
orer/ecosystems/be_an_explorer/map/for
m_caterpillars.htm#
Section 1.4 Ecology (Higher Level)
What you should learn about
today..
• Definitions and examples of parasitism
• Definitions and examples of symbiosis
Section 1.4 Ecology (Higher Level)
Symbiosis
• Symbiosis occurs when two organisms live in close
association and at least one of them benefits.
Example: Nitrogen fixing bacteria in nodules of plants
• Bacteria provides nitrates for the plant
• Plant provides the bacteria with food and shelter
Section 1.4 Ecology (Higher Level)
Parasitism
Def Parasitism occurs when two organisms live in close
association and one organism (the parasite) gets its
food from another organism (the host) and does is
harm in the process.
Example:
Fleas on a dog!
Section 1.4 Ecology (Higher Level)
Which one?
The clownfish can come in
contact with the stinging
tentacles of the sea anemone
and not be harmed by them. At
the same time, it receives
protection from its enemies. The
clownfish feeds the anemone by
gathering nutrients and also
leaving nutritional waste on the
tentacles.
Section 1.4 Ecology (Higher Level)
Which one ?
• Tapeworms, for example, have no gut, so
that they rely on their host to provide them
with already digested food.
Section 1.4 Ecology (Higher Level)
• the hermit crab and a sea anemone
• The anemone is often found attached to the shell in which the
hermit crab lives. Often, a sea anemone attaches itself to the crab's
shelter and it may envelop part of the crab's own shell as well. As
the crab moves about in search of food the anemone is brought into
contact with a greater supply of food and the crab is protected by the
anemone's stinging cells.
Section 1.4 Ecology (Higher Level)
• A familiar wildlife scene in Africa is that of
oxpeckers running over the backs of
rhinoceroses. These birds rid their
partners of injurious and annoying pests
and in doing so obtain a ready supply of
food
Section 1.4 Ecology (Higher Level)
What did you learn about population dynamics today?
Section 1.4 Ecology (Higher Level)
POPULATION DYNAMICS
• DEPTH OF TREATMENT
1.Students should be capable of outlining
the contributory factors or variables in
predator/prey relationships
2.Factors that affect human population
numbers
3.Current human population figures and
explanations
Section 1.4 Ecology (Higher Level)
Population Dynamics
• About the factors that cause population
numbers to change.
Section 1.4 Ecology (Higher Level)
Predator and prey relationships
1.prey has
food and
numbers
increase as
they breed
2.numbers of predators
increase as they more
food to eat and breed.
5. When there are
less predators around
the number of prey
rise again!
Time
3. Once predator numbers
rise more prey are killed the number of prey starts
to fall
4. When prey numbers drop,
the predators have less food
and their numbers drop- they
starve or migrate
Section 1.4 Ecology (Higher Level)
Factors that contribute to prey
and predator relationships
Food
If numbers of prey drop predators have ______ food and numbers
__________
If numbers of predators decrease the numbers of prey will ____________
Concealment
If prey can hide from predators they can prevent getting killed and
numbers __________________
Migration
If predators leave an area, the numbers of prey_____________________
Section 1.4 Ecology (Higher Level)
Factors that effect the human population
How will each of the following effect
human population numbers?
1. war
2. famine
3. contraception
4. disease.
Section 1.4 Ecology (Higher Level)
1. War
Reduces population due to
death.
Currently 800 people in the
world die every day due to war
Section 1.4 Ecology (Higher Level)
2. Famine
An extreme and
ongoing lack of food
causes a famine.
Causes population
numbers to decrease.
Section 1.4 Ecology (Higher Level)
3. Contraception
Any human intervention that
stops births.
Reduces population numbers.
The increased availability of
contraceptives has reduced
birth rates since the 1960s.
Section 1.4 Ecology (Higher Level)
4. Disease
Bacterial and viral diseases can
kill people and cause a lack of
food or clean water.
Despite the availability of
medicines for many diseases
many people still can’t afford
them
Section 1.4 Ecology (Higher Level)
Human Population
The human population is about 6 billion and still growing!
Section 1.4 Ecology (Higher Level)
Why is the population growing so
fast?
• Improved public health
water supplies and waste removal
• Better medical care –
vaccinations and antibiotics readily
available for lots of people.
• Improved agriculture
domesticated plants and animals- more
food !
Section 1.4 Ecology (Higher Level)
Did you learn…
1.Students should be capable of outlining
the contributory factors or variables in
predator/prey relationships
2.Factors that affect human population
numbers
3.Current human population figures and
explanations