Download Unit 3 Life on Earth Miss Pearce

1. Biodiversity and
Human Impacts
2. Sampling Techniques
3. Energy Flow
4. Evolution
Topic 1
Biodiversity Key Terms
Term
Definition
Biodiversity
Variety of living organisms on Earth.
Biomes
Regions of our planet as distinguished by their
similar climate, flora and fauna e.g. tundra
Habitat
Place an organism lives.
Ecosystem
Habitat + Community
Community
All the living organisms in an area.
Population
A group of living organisms of the one type e.g.
dogs
Species
A group of living organisms which are able to
interbreed to produce fertile offspring.
Niche
Description of organisms lifestyle/ Role it
plays.
Biodiversity
•
Biodiversity is the term used to describe the variety of
living things in an ecosystem.
• Various
factors can affect the biodiversity within an
ecosystem, some of which include;
- Abiotic factors
- Biotic factors
- Human influences
- Natural hazards
• It
is important that Biologists keep a close eye on
Biodiversity as ecosystems are delicately balanced.
Understanding Biomes
Earth is divided into distinct climate zones called
BIOMES.
• Each biomes contains it’s own animals (fauna), plants
(flora) and climate (temperature and rainfall).
• Plants and animals within these biomes are specially
adapted to survive in their surroundings.
•
• THINK!
What animals/plants do you find in the tropical
rainforest? Are these the same in the desert or the
polar regions on earth? Discuss why!
Niches
•A
NICHE is the term used to describe the
lifestyle/ role that an organism plays within its
ecosystem.
• Factors
to consider when describing a niche
include:
- How that particular organism affects/is
affected by other things around it
- How it survives/competes
•
NICHES OFTEN COME UP AS EXAM MCQs
Human Influences: Air Pollution
• Car
exhaust fumes contain sulphur dioxide and nitrogen
oxides (NOx gases) which combine with rain water to form
acid rain.
• THINK!
Why is acid rain problematic? Discuss.
Human Influences: Deforestation
• Deforestation
is the clearing of vast areas of
natural forest without replanting replacement
forests.
• There
are many severe consequences of
deforestation:
- habitat destruction for many organisms
- low-lying downstream areas become flooded
- reduced soil fertility of hillsides
- higher levels of CO2 contribute to
greenhouse effect (climate change)
Human Influences:
Intensive Agriculture
• Farmers
create conditions that favour one or two chosen
kind of crop plants and thus reduce the natural
biodiversity.
• Farmers
will do this by using:
• Herbicides to kill other plants
• Pesticides to kill pests that reduce crop value
• Fertilisers that favour the chosen crop
• Planting GM Crops
• Remove hedges for easier harvesting
Effect of Human Influences
• Human
activities, e.g. pollution, habitat
destruction and over hunting, are to blame for
the current wave of extinctions.
• Currently,
extinction is happening x400 than
the natural rate
• There
are several different species
threatened with extinction today including;
Black Rhino
Endangered
Californian Condor
California
Condor
Endangered
Giant
Panda
Endangered
Snow Leopard
Endangered
Blue
Whale
Endangered
Tiger
Mountain
Endangered
Gorilla
Topic 2
Sampling Key Terms
Abiotic Factors
(Non-living factors)
Temperature
Light Intensity
Biotic Factors
(Living factors)
Predation
Disease
Soil Moisture
pH of Soil
Grazing
Food Availability
Abiotic Sampling
• Abiotic
factors are the NON-LIVING components
of any ecosystem.
• Experimental sampling of abiotic factors requires
good technique to avoid errors whilst using the
equipment.
• Just as with any experiment it is fundamental
that the readings are Repeated for Reliable
Results.
Abiotic Sampling:
Equipment and Errors
Abiotic Factor Equipment Required
Avoiding Error
Temperature
Leave thermometer to settle for a
few minutes before taking a reading.
Thermometer
Experiment 1: Abiotic Sampling
Light Intensity Light Intensity Meter Do not cast a shadow over the solar
Take equipment into
grounds and
panel. Stand to the side when
sample 3 differenttaking
areas
for
readings.
comparison.
pH of Soil
Soil pH Meter
Wipe the probe clean between
Note your results samples
in your
jotters.
to prevent
any cross
contamination.
Soil Moisture
Soil Moisture Meter
Wipe the probe clean between
samples to prevent cross
contamination.
ERRORS/ PREVENTIONS OFTEN EXAM QUESTIONS
Biotic Sampling:
Equipment and Errors
• Biotic
factors are the LIVING components of
any ecosystem. The method used to sample the
organisms depends on the type of species being
studied.
• Experimental sampling of biotic factors
requires good technique and set up of
equipment to avoid errors.
Biotic Sampling: Pitfall Traps
• Pitfall
traps are a simple method which is used to sample small
invertebrates such as insects found in leaf litter/on the floor
of woodland etc.
is essential
that the cup
buriedSampling
level with the soil
Experiment
2:isBiotic
surface andTake
is wellequipment
camouflaged
with
leafs. and
into
grounds
• It
Why
is up
it important
to camouflage
set
your pitfall
traps in the top of the cup?
What othervarious
problemsareas.
might arise? Are there any
types of insects
which
this method
is NOT
suitable
We will
return
to them
tomorrow
for sampling? Discuss.
• THINK!
for the results.
Biotic Sampling: Quadrats
• For
plants and animals which don't move much (i.e.
limpets) quadrats are normally used to sample their
numbers in an area.
Experiment 3: Biotic Sampling
• Quadrats must
repeatedly
thrown
RANDOMLY
in the
Takebe
equipment
into
grounds*
and
area for reliable results.
sample the field with your
• Sources ofquadrat.
error include the difficulty in identifying the
species present
or not to include a
Note and
any deciding
findings whether
in your jotters.
plant which*Weather
is partially
present in the grid.
depending
Biotic Sampling: Other Methods
• Other
ways of
sampling living
organisms that
you should be
aware of include;
- Tree Beating
- Tulgren Funnel
- Transect
- Water Net
Topic 3
Energy Flow Key Terms
Term
Definition
Herbivore
Animal which only eats plants
Omnivore
Animal which eats both plants and other
animals
Carnivore
Animal which only eats other animals
Intraspecific
Competition
Competition between the SAME species
Interspecific
Competition
Competition between DIFFERENT species
Pyramid of Numbers
Pictorial diagram showing the relative
numbers of each organism in a food chain.
Pyramid of Biomass
Pictorial diagram showing the relative DRY
MASS of each organism in a food chain.
Pyramid of Energy
Pictorial diagram showing the relative energy
at each level in the food chain.
Energy Flow: Food Chains
• Food
chains show the DIRECTION of energy flow from producer
(green plants) to consumer.
• Only
• The
10% of energy is passed on at each level in a food chain.
other 90% is used in cellular processes, movement,
homeostasis (temperature regulation) and excreted as waste.
Energy Flow: Food Webs
• Food webs are different from
food chains as they show
intraspecific competition over
food sources thus providing a
more complete picture of the
4: Owl Pellet Dissection
energyExperiment
flow.
Tease apart the owl pellet to find out
what it has eaten!
FOOD WEB EXAM QUs WILL ALWAYS ASK HOW ONE
SPECIES AFFECT ANOTHER (BALANCE)
Working with Pyramids
• Pyramids
are used by Biologists to highlight in a pictorial
fashion what information they can gather about food
chains.
• Pyramids
of numbers represent how many of each
organism there are in one food chain whilst Pyramids of
Biomass show the DRY mass of each organism in a food
chain.
• The
shape of these pyramids often form a classic
triangle however there are exceptions for number
pyramids e.g. when parasites are present or when a large
tree is the initial producer.
Pyramid Shape Examples
1. Parasites Present
2. Tree as Producer
3. Classic Example
Energy Flow: Nitrogen Cycle
• It
is essential that Nitrogen is recycled
between food webs and the ecosystem
(Circle of Life).
• Nitrogen is needed to make PROTEINS
but cannot be absorbed in gaseous form
by plants or animals.
• Plants must absorb Nitrogen in the form
of NITRATES from the soil as shown in
the Nitrogen cycle on the next slide.
The Nitrogen Cycle
Experiment 5: Root Nodules
Prove that nitrifying bacteria can be
found in root nodules by growing
them on nitrogen free agar plates!
Type of Bacteria
Role in Nitrogen Cycle
Decomposers
Decompose (breakdown)
the nitrogen found in
dead bodies and waste
into ammonium
Convert ammonium into
nitrites and then into
nitrates
Nitrifying
Denitrifying
Breakdown nitrates
releasing nitrogen gas
into the air
Nitrogen Fixing
‘Fix’ nitrogen gas from
the air into nitrates or
protein
Over Use of Fertilisers
• Farmers
often use
fertilisers to increase the
nutrients in their soil;
particularly Nitrogen.
• Many
problems can arise
due to fertiliser over-use;
in particular
EUTROPHICATION due
to nutrients feeding
bacteria and causing
ALGAL BLOOMS which
lead to DECREASED
BIODIVERSITY.
4 MARK EXAM QU.
MAKE SURE YOU KNOW THE
NITROGEN CYCLE AND
PROBLEMS!!
Topic 4
Adapt, Nat Selection & Evolution
Key Terms
Term
Definition
Mutation
A random change to genetic material
(DNA)
Adaptation
An inherited characteristic that
makes an organism suited to its
environment
Natural Selection
Favourable alleles (genes) are passed
on to the next generation.
Evolution
Changes which have occurred over
long periods of time to develop new
species from one common ancestor.
Adaptations
THINK! What are the ADAPTATIONS on the
following examples?
Are they STRUCTURAL/ BEHAVIOURAL?
Example 1: Cactus
Example 2: Polar Bear
Adaptations
• Adaptations
can arise from a mutation which covets
survival.
• Mutations can be advantageous, neutral or
disadvantageous.
• The rate at which mutations appear can be affected by :
1. Exposure to high temperatures
2. Exposure to radiation
3. Exposure to chemicals.
• THINK!
Can you think of any mutations in humans which
are advantageous/neutral or disadvantageous?
Discuss.
Natural Selection
• Natural
selection is when alleles (genes) which are
favorable to the survival of the species are passed on to
the next generation.
• The classic example is the peppered moth in Britain:
- White form original (1800s)
- Industrial revolution
- Soot covered trees
- Mutation for colour arose
- Black form survived predation
- Decrease in pollution
means both forms exist today
Evolution (Speciation)
• There
are 4 key stages to the evolution of a species.