Download Life on Earth

Success criteria
 I can define terms associated with
ecosystems.
 I can construct and describe food
chains/webs.
 I can describe pyramids of numbers.
 I can describe the two types of
competition.
Producer & Consumers
All organisms in our world are connected
to each other & termed
1. Producers
2. Consumers
Producers
Producers make their food by a process
called photosynthesis.
Food Chain
• The way in which organisms interact can
be shown by a food chain.
Food Chains
• The arrows show the direction of
energy flow.
(primary
consumer)
(secondary
consumer)
The 1st consumer is called the primary consumer
The 2nd consumer is called the secondary consumer
Energy loss in Food chains
• Only 10% of energy is passed on to next
level in a food chain.
Energy loss in Food chains
Most of the energy is lost as:
A) Heat
B) Movement
C) Undigested material
Calculation
1000 units of energy in grass – how much
energy does the owl receive?
Calculation
1000 units of energy in grass – how much
energy does the owl receive?
1000
100
10
1
Key word
Definition
Consumer
Omnivore
Carnivore
Herbivore
Prey
Predator
Producer
Eats another organism
Eats animals and plants
Only eats other animals
Only eats plants
Gets eaten by the predator
Feeds on the prey
Makes its own food by
photosynthesis
Food webs
Animals usually eat many different things and
are involved in lots of different food chains.
These more complicated feeding relationships
can be shown in a food web.
How many simple food chains can you see in
this food web?
Analysing food webs
What would happen to the _________ if the
________ died out?
Increase or decrease – why?
There is a lot of competition for
resources among organisms in a food web.
Interspecific vs. Intraspecific
Between
organisms of
different
species for
similar
resources.
Between
organisms of
the same
species for the
same resources.
There is a lot of competition for
resources among organisms in a food web.
Animals compete for...
• Food
• Mates
• Habitats
Plants compete for...
• Nutrients
• Water
• Space
1. Pyramid of biomass
BLACKBIRD
LADYBIRD
GREEN FLY
ROSE BUSH
Shows the total mass of
organisms at each stage of a
food chain
2. Pyramid of Energy
BLACKBIRD
LADYBIRD
GREEN FLY
ROSE BUSH
Shows the total energy received by
organisms at each stage of a food
chain
3. Pyramid of Numbers
Show the total number of organisms at
each stage of a food chain
1 fox
Small numbers of
large organisms
30 Rabbits
100,000 blades of grass
Large numbers of
small organisms
Problems with Pyramids of Numbers
What if tree is the producer?
Oak tree
greenfly
wasp
blue tit
What if insects are the top consumer?
Grass
zebra
lion
flea
Oak tree
Greenfly
Finch
Pyramid of numbers = not always
a pyramid!
L
Success criteria
 I can define terms associated with ecosystems.
 I can construct and describe food chains/webs.
 I can describe the two types of competition.
 I can describe pyramids of
numbers/energy/biomass.
The
Nitrogen
Cycle
 About 78% of the air consists of nitrogen gas.
 All living things need nitrogen to make proteins
(e.g. enzymes, hormones, antibodies, etc.).
 Plants and animals cannot use nitrogen gas
directly.
 Plants absorb it in the soil in the form of
nitrate.
 Animals then eat plants or other animals to get
their supply of nitrogen.
Excretion
and death
Nutrients in
living
organisms
Absorption
by living
things
Nutrients
dead bodies
and waste
Nutrients in
the
environment
available
for use
Decomposition
by bacteria
and fungi
Nitrogen Cycle – 4 main
stages
1.
Decomposition – fungi break down
dead organisms and waste, releasing
ammonia into the soil.
Nitrogen Cycle – 4 main
stages
2.
Nitrification - nitrifying bacteria
convert ammonia to nitrites, and then
nitrites into nitrates that can be used
by a plant.
Nitrogen Cycle – 4 main
stages
3.
Denitrification – denitrifying
bacteria deprive the soil nitrates by
breaking down the nitrates and
releasing nitrogen gas into the air.
Nitrogen Cycle – 4 main
stages
4.
Nitrogen fixation – nitrogen fixing
bacteria absorb nitrogen gas and
‘fix’ it back into nitrate. Nitrogen
fixing bacteria can either be found
in the soil or in the root nodules of
legume plants.
3 Main Bacteria
Nitrifying Bacteria
Ammonia
Nitrite
Nitrate
Denitrifying Bacteria
Nitrate
Nitrogen gas
Nitrogen Fixing bacteria
Nitrogen gas
nitrate/protein
Which letter(s) shows;
1. The decay of dead
material
B
2. Nitrification
C, D
3. Nitrogen fixation
G
Complete the table below by filling in a description of each stage.
Stage
Absorption
Eating
Decomposition
Bacteria
involved?
None
None
Decomposing
bacteria or fungi
Nitrification
Nitrifying
bacteria
Denitrification
Denitrifying
bacteria
Nitrogen fixation Nitrogen fixing
bacteria
Description
Success criteria
 I can describe what a biome is.
 I can name several types of biomes.
 I can state the effect of abiotic
factors on the distribution of biomes.
Biodiversity
Variety and abundance of all living organisms.
Importance of biodiversity;
Variety of organisms is important so that
they can adapt to changing environment
conditions.
Habitat
Where the animals/plants live.
Community
All the organisms living together.
Population
The number of ONE species living in an area.
Ecosystem
An area made up of living & non living
parts.
What is a biome?
Large ecosystem consisting of distinctive:
a) Flora (plants)
b) Fauna (animal)
c) Climate
Main factors affecting global
distribution of biomes:
Rainfall
Temperature
Success criteria
 I can describe the main factors affecting
biodiversity.
 I can list several biotic and abiotic factors.
 I can describe the sampling techniques used to
measure various biotic and abiotic factors.
 I can explain how to minimise possible sources
of error when carrying out sampling techniques.
Factors affecting
biodiversity
1. Biotic
(living)
2. Abiotic
(non-living)
3. Human
impact
(what we do)
Biotic factors
Living factors affecting biodiversity;
1.
2.
3.
4.
5.
Predation
Grazing
Disease
Competition
Food availability
Predator/Prey Graphs
Abiotic factors
Non-living factors affecting biodiversity;
1.
2.
3.
4.
Temperature
Light intensity
pH
Moisture
Human Impact
Biggest factor in reducing biodiversity and
distribution of biomes.
e.g.
•
•
•
•
•
•
Over hunting
Over fishing
Habitat destruction (deforestation)
Poaching endangered species
Air pollution (from burning fossil fuels)
Water pollution
Sampling Techniques
Techniques used to measure various
biotic and abiotic factors in the
environment.
Animals
1. Pitfall traps
2. Tree beating
Plants
1. Quadrats
Quadrats
 Thrown at random (not placed down).
 Don’t count number of flowers, count
number of squares the flower is in.
 Repeat for increased reliability.
Errors with quadrats
 Not thrown randomly
(throw randomly)
 Organisms wrongly
identified
(use key)
Pitfall Trap
(e.g. woodlouse)
 Hole dug level with ground.
 Covered with stones, leaves.
 Checked regularly.
Errors with pitfall traps
 Hole not level with ground – insects
won’t fall in.
 Trap not hidden – insects will avoid
the trap.
 Not checked regularly – insects could
eat each other.
Tree Beating
(e.g. spiders)
 Branch given few sharp taps at specific
height.
 Small animals drop onto tray with raised
edges below to stop insects crawling out.
 Repeat for more reliability.
Errors with tree
beating
 Insects fly out of bucket.
(could use a bucket with rimmed edge)
 Insects do not fall into bucket.
(use larger bucket)
Abiotic sampling techniques
1. Light intensity
2. Moisture
3. pH
4. Temperature
Light intensity
 Measured with a light meter.
 Hold the light meter arms distance
away so that you don’t cast a shadow
over it.
 Point at maximum light.
Errors with light
intensity
 Accidentally
shading the light
meter.
Moisture or pH
 Measured with a moisture meter/pH
meter.
 Push the probe into the soil and read
the meter.
Errors with moisture or pH
 Not wiping pH meter/moisture meter
probes between readings.
General rule;
Results are made more reliable
by taking many samples
(REPEATING experiment).
Line Transects
Looking at the effect of an abiotic
factor on the distribution of plant
growth.
Example;
light intensity on plant growth
Quadrat placed every meter – NOT
THROWN RANDOMLY!!!
Success criteria
 I can describe the purpose of a paired
statement key.
 I can use a paired statement key to
identify organisms.
 I can construct a paired statement key
to allow others to identify unknown
organisms.
Identifying Organisms
 It’s all very well counting/collecting
organisms, but not all of them will be
familiar to us.
 To identify unfamiliar organisms, we
would use a key.
 There are different kinds of key.
Branching Key
Animals
No legs
Legs
8 legs
Spider
More than 8
legs
Centipede
Shell
Snail
No shell
Earthworm
Paired Statement Keys
 Paired statement keys work in the
same way as branching keys.
 At each stage you are given a choice.
 Make the appropriate choice and go
to where you are asked to go.
 Again, if the organism is present, you
should end up with a name for it.
Success criteria
 I can describe a what a mutation is, and
how they occur.
 I can give examples of advantageous,
disadvantageous and neutral mutations.
 I can state the importance of variation.
 I can define and give examples of
mutagenic agents.
Mutation
Random Change to
DNA bases.
Mutations are:
Randomly Occurring
Low frequency (ROLF)
Mutation Types
1.
Disadvantage (genetic disease)
2.
Advantage (new variety of species)
3.
Neutral
Genetic Disease: Down Syndrome
 3 copies of chromosome 21 (instead of
just 2).
 Occurs in 1 in every 1,000 children
born each year.
Advantageous Mutations
 Mutations create variety (new
alleles).
 Variation helps animals or plants
cope with environmental change.
Example:
Peppered moth
Neutral Mutations
Changes in DNA bases that are
neither beneficial nor detrimental to
the ability of an organism to survive
and reproduce.
E.g. different coloured eyes
Mutagenic Agents
Increase the frequency of a mutation
occurring.
Examples include;
1. X-rays
2. UV radiation
3. Mustard gas
4. High temperatures
1. X-rays
2. UV radiation
3. Mustard gas
Success criteria
 I can describe the 2 main types of
adaptations, and give examples of each.
 I can describe Darwin’s Theory of
Evolution.
 I can explain the term ‘survival of the
fittest’.
Adaptations
Mutations (increased variety)
allows organisms to adapt to be
better suited to their
environment/cope with
environmental change.
Most adaptations are either:
Structural
Involve
specialized
structures
possessed by
the organism.
Behavioural
Depends on the
way the
organism
behaves.
Adaptations of the
desert rat
Burrowing into sand
when temperature is
too high.
Behavioural
Large back
feet help them
to jump away
from
predators.
Structural
Adaptations of the
cactus
The leaves are
reduced to spines in
order to decrease
the surface area for
water loss.
Vast root
system to
maximise
water
uptake.
Structural
Adaptations of the camel
Rest during the day
when the
temperatures in the
desert are very high.
Behavioural
Humps store
fat which
produces water
when
metabolised.
Structural
The theory of evolution states
that evolution happens by natural
selection.
Key points:
 Individuals in a species show a wide range
of variation.
 Individuals with characteristics most suited
to the environment are more likely to
survive and reproduce.
 The genes that allowed the individuals to be
successful are passed to the offspring in
the next generation.
Darwin’s Theory of Evolution
“Survival of the
fittest”
Natural Selection
The organism best suited to the
environment survive.
Natural Selection
There is natural variation in the
population.
Natural Selection
Those with the selective advantage
for survival increase in population.
Natural Selection
These organisms are able to breed and
pass on their desirable genes.
Natural Selection
Organisms without the selective
advantage die out.
Likely exam
question!
Q. Explain the concept of “survival of the fittest”. (2)
Natural Selection chooses organisms that
have a SELECTIVE ADVANTAGE for
survival who then reproduce & pass on
successful alleles.
Success criteria
 I can define the term ‘species’.
 I can describe the different stages
involved in the process of speciation.
 I can state the importance of isolating
mechanisms, and give some examples of
different types.
What is a species?
A group of related organisms that
interbreed & produce fertile offspring.
Horses and donkeys are closely related,
and look very similar, but they are
members of different species.
Horses mate
with each
other to
produce young
horses, which
themselves
will be able to
mate (fertile).
Donkeys can
mate with each
other to produce
young donkeys,
which
themselves will
be able to mate
(fertile).
If a donkey mates with a horse, they
produce a mule, which is infertile and
cannot mate to produce offspring.
Fertile
Fertile
Infertile
Speciation
Creating a new
species.
Speciation – 3 stages
1. Isolating Mechanism
2. Mutations
3. Natural Selection
New species formed!
One species of
organism.
The species is split
into 2 subpopulations,
separated by an
isolating mechanism.
The isolating
mechanism prevents
gene flow across
sub-populations.
A random mutation
(low frequency)
occurs on one side
of the barrier.
Natural Selection
chooses
organisms that
have a selective
advantage for
survival, who then
reproduce & pass
on successful
alleles.
A new species is formed. This new
species cannot interbreed with the
original species to produce fertile
offspring (even if the barrier is
removed).
Types of Isolating
Mechanisms
1. Geographical
2. Ecological
3. Reproductive
Importance of isolating
mechanisms
Prevents gene flow (exchange of
genes) between sub-populations.
Free flow of
genes
between all
population
4
Population 3 becomes extinct
1
Flow of
genes only 1
to 2
3
2
1
2
4
Population 4
becomes
isolated
How many
species?
How many
species?
Isolating
mechanism
Common error in ‘isolating mechanism’
answer
“the barrier separates different
species”.
Barriers separate groups of the
same species, which then undergo
mutation and natural selection until
they become separate species.
Past paper question
A.
B.
C.
D.
Quick recap…
1. Isolation
2. Mutation
3. Natural
selection
Speciation!
Just
remember……
I’m a new
species.
Success criteria
 I can describe the advantages and
disadvantages of intensive farming.
 I can explain the problems caused by
pesticides and fertilisers.
 I can describe the role of indicator species
in an environment.
 I can describe biological control and genetic
modification.
What’s the problem?
Not enough food to feed everyone.
Food Science Challenge
Need to increase yield of crops grown.
Solution?
1. Intensive Farming
2. Biological Control
3. Genetically
Modified (GM) Crops
Advantages of Intensive Farming
Increased yield making food more
affordable/available.
Features of Intensive Farming
Fertilisers
Nutrients to help
crops grow (nitrates).
Pesticides
To kill pests
that eat crops.
Problems with pesticides
Pesticides aren’t broken down, so they
build up at each stage of the food chain.
This can be toxic for the predators at
the top of the food chain.
Problems with fertilisers
Creates algae bloom in water.
Disadvantage of fertilisers
1. Fertiliser washes into rivers from fields.
2. Increased algae bloom.
3. Increased bacteria as they feed on algae.
4. Decreased oxygen levels (all the bacteria
use the oxygen for respiration).
5. Decreased biodiversity.
Intensive Farming Summary
1. Algae bloom
Deoxygenates water as bacteria that
feed on algae use up oxygen and reduce
biodiversity.
2. Pesticide build up (DDT)
DDT builds up to toxic levels in food
chains.
Pesticide resistance.
Indicator Species
A species whose presence/absence
indicates level of pollution in environment.
Lichen only grows
where there is
little air pollution
(little SO2).
Indicator Species Example
Stone fly nymph
Only present in high
oxygen levels in water
(no algae bloom).
Biological Control
Natural method of control (no chemicals).
a) Using predator
b) Deliberately introducing a disease
Ladybirds and greenfly
Myxoma virus and myxomatosis in
Australian rabbits
Advantages
1. No chemicals so no algae bloom/pesticides
building up.
2. Cheap after initial set up costs.
Disadvantages
1. Can’t guarantee that all pests will be
killed.
2. Predator or disease could become the
problem in place of the pest.
Genetic Modification
Genetic Engineering
(Cell Biology unit)
A useful gene from another species is
inserted into the plant to produce a GM
crop.
GM cauliflowers grown with scorpion
genes that kill pests that try to eat
the cauliflower.
Golden Rice