Transcript Factors affecting population size

Biosphere
SG Biology
How it works?
The Biosphere
Investigating an ecosystem
Sampling and other measurement techniques applied
to the investigation of an ecosystem.
How it works
Components of an ecosystem,
energy flow,
population growth,
controlling factors.
Control and management
Intervention in the natural balance of an ecosystem;
using understanding to manage ecosystems.
Identification
Think of a species (plant or animal)
Write down a description of your
species on a piece of card.
Exchange the card with another
member of the class.
Could they identify the species you
have described?
Identification keys
Identification keys help us to identify
plants and animals. Have a look at the
samples of keys available in class.
The two types of key you could use are:
Numerical key
Branched key
Complete the worksheet on identification
keys
Food Chains
Watch the Scientific Eye video
making notes on food chains, and
factors affecting populations.
Food Chains and Food
Webs
Environment and Feeding
Definitions
Herbivore:
An animal that eats grass and other green
plants in a food chain;
Carnivore:
A flesh-eating animal.
Prey:
An animal hunted or caught for food
Predator:
An organism that lives by preying on other
organisms.
Definitions
Primary consumer:
An animal that eats grass and other green plants
in a food chain; an herbivore.
Secondary consumer:
An animal that feeds on smaller plant-eating
animals in a food chain.
tertiary consumer:
An animal that feeds on secondary consumers in
a food chain.
Population:
All the organisms of the same species living in the
same place at the same time.
Food Chains
Food chains are one way of showing how
organisms interact. For example:
Grass

Rabbit

Fox
The arrows represent the flow of energy
(food) between organisms, it points from
the eaten to the eater.
All food chains start with plants, they
use sunlight during photosynthesis to
build up food (energy) stores, these
are then passed on to animals.
Important terms:
Plants are producers because they
produce their own food
Animals are consumers because they
eat food to obtain energy.
There are 3 types of consumer
Herbivores eat plants
Carnivores eat other animals
Omnivores eat plants and animals
Organisms that breakdown dead plants
and animals are called decomposers, e.g.
fungi, bacteria and worms
Producer
PLANTS
 primary
consumer
HERBIVORE

secondary
consumer
CARNIVORE

tertiary
consumer
TOP
CARNIVORE
Food Webs
When several food chains in a
habitat are studied, some organisms
appear in more than one.
This is because most animals eat
more than one type of food.
If food chains in a habitat are linked,
they form a FOOD WEB.
Food web for a single tree
Which are the primary and secondary
consumers in this photograph?
Competing for the same
niche
Biosphere
How it works?
Populations
Adaptations
Factors affecting population size
Populations
A population is a group of
individuals of the same species living
in a particular habitat at the same
time.
The number of individuals present in
the population will depend on how
they can interact with two types of
factor.
Populations
Living factors – food, disease,
predation, mates, effects of
humans, and competition
Non-living factors – water, oxygen,
carbon dioxide, temperature and
light
Competition for Resources
Plants and animals compete for
resources.
Plants often compete with each other for
space, and for nutrients and water from the
soil.
Animals often compete with each other for
space, water and food.
Competition for Resources
There are two types of competition:
Intra-specific – competition between
individuals of the same species
Red deer stags fight to
mate with the females
Boobies compete for
nesting space
Competition for Resources
Inter-specific – competition between
individuals of different species.
Garden birds
compete for
food in winter
Plants compete
for space, light,
water and
nutrients.
Factors affecting population size
A population is a group of individuals
of the same species living in a
particular habitat.
Births and immigration increase the
size of a population.
Deaths and emigration decrease the
size of a population.
Factors affecting population size
The size of a population, may also
be affected by:
The total amount of food and water
available, if food supply is low, then
individuals will compete for them.
Oxygen shortage can limit numbers in
a population that lives in water.
Poisons can build up in the
environment and limit population
growth.
Factors affecting population size
List continued from previous page:
Predation will limit the prey population.
Disease can spread quickly through
large populations.
Climate – drought, flood and storms all
affect population numbers.
Lack of shelter
Competition for light
Population Graphs
For one species in good conditions
4
Number of
individuals
3
2
1
time
For one population in good condition
1. Slow increase as only a few
individuals.
2. Sharp increase, good conditions
for growth
3. Some factors start to slow down
increase (e.g. lack of food).
4. Stable population (birth rate =
death rate)
Predator-prey relationships
Animals that kill and eat other animals are
called predators. The animals that they
eat are called prey.
Predators are usually bigger and fewer in
number than their prey.
List five things that make a good
predator:
List five ways prey have adapted escape
from predators:
The graph shows the relationship
between a predator and its prey.
List what is happening in each of
the stages 1 – 5 on the predator
prey graph.
1.
2.
3.
The prey has plenty of food. It breeds
and increases in number.
The increase in prey means that there is
more food for the predator. So the
predator breeds and increases in
number.
There are now lots of predators so more
prey will be eaten. The number of prey
goes down.
Predator prey graph
There are now less prey for the predator
to feed on. Food will be scarce and
many predators starve.
5. With fewer predators, more prey survive
to breed. The prey numbers increase
4.
The cycle continues…
Adaptation
The Biosphere
How it works?
Learning Outcomes
To explain the terms ecosystem,
habitat and community.
To understand that physical factors
affect animals living in an ecosystem
To be able to explain how animals
are adapted for survival in arctic
and desert conditions.
What is an Ecosystem?
The Environment
An ecosystem is an environment where living
organisms can survive.
The environment is made up of lots of different
ecosystems, such as seashore, a wood or a river.
Each ecosystem is made up Habitats and
Communities
Habitat - This is the place where the organisms
live. It has the conditions that they need to
survive.
Community – all the living organisms that live in
the habitat.
Physical Factors
Each ecosystem has a set of
environmental factors.
Availability of water
Temperature - Few living organisms can grow
outside the range of 0oC to 40oC.
amount of Light - photosynthesis in plants,
animals need light for visibility.
Availability of carbon dioxide and oxygen
These factors vary according to the time
of day and the time of year.
Adaptations
Living things adapt to their
environment.
Watch the video clip, and then try
to fill in the table explaining how the
creature is adapted to it’s
environment.
Adaptations in different
animals
Look at the animals on the
worksheet, for each one try to give
where it lives and an example of
how it is adapted for survival in its
environment.
Pupil Activity
Surviving in different environments.
Read all information carefully
Answer questions 1 - 9
Camel
designed for desert conditions
A camel’s hump is a
fat store. It can
break down fat to
release water.
A camel can
drink large
amounts of
water.
Its mouth is
tough so that it
can eat thorny
plants like cacti.
Short hair
underneath the camel
lets heat escape.
Coarse wool on
top of its body
protects the
camel from the
sun.
Big flat feet
stop it
sinking into
the sand.
Adaptations to water loss
a cactus in the desert
Leaves reduced to spines – to reduce water loss
through stoma
Swollen stem
stores water
Wide spread root
systems to increase
surface area for absorption.
Camel – designed for desert conditions
A camel’s hump is a
fat store. It can
break down fat to
release water.
A camel can
drink large
amounts of
water.
Its mouth is
tough so that it
can eat thorny
plants like cacti.
Short hair
underneath the camel
lets heat escape.
Coarse wool on
top of its body
protects the
camel from the
sun.
Big flat feet
stop it
sinking into
the sand.
Adaptations to water loss
- a cactus in the desert
Leaves reduced to spines – to reduce water
loss through stoma
Swollen stem
stores water
Wide spread root
systems to increase
surface area for absorption.
Class activity
To draw labelled diagrams of a cactus, a
camel and a polar bear which explain
how they are adapted to their
environment.
Use one side of your exercise book for
each diagram, and labels.
Use the handouts to help you with the
labels.
Commendations will be awarded for
exceptional work!
Pupil Activity - extension
Environmental factors affecting life
Read all the information supplied on
the sheet carefully.
Answer questions 1 – 11 in full
sentences.