Heterotroph : gains energy by consuming other organisms
Ecology: the study of interactions between
organisms and their environment
Population: all organisms of 1 species that reside
in the same space
Habitat: where an organism lives
Community: a space where many different
species reside at the same time. They interact
together
Autotroph: An organism that can manufacture its own
energy from inorganic substances or light
Niche: The role of an organism within an ecosystem
including where it lives, what it eats and its effect on the
ecosystem
Biome: A category within the biosphere
containing all the plants and animals in a region
Trophic levels: a level in a food
chain defined by the method of
obtaining food
1. PRODUCERS: the plants and photosynthetic organisms
2. PRIMARY CONSUMERS: Herbivores 3. SECONDARY
CONSUMERS: Carnivores 4. DECOMPOSERS: feeds on waste
materials or dead organisms
As you go up the food chain, less energy is
available. However, it is more energy efficient for
people to consume carnivores because humans
can’t fully digest all of a plant due to the cellulose
At higher tropic levels, there are fewer individuals
because: - More needs to be consumed to meet
their energy demands - More completion
Pyramid of Numbers: The area of the bars are
proportional to the number of organisms at each
stage
Pyramid of biomass: To obtain this data,
organisms are all collected and burnt so that all
the water has evaporated and only the tissue
mass remains.. The area of the bar is proportional
to the dry mass of all the organisms at that tropic
level
Pyramid of energy: To obstain this data, all
organisms are burnt in a calorimeter and the heat
energy omitted from this is measured
Energy Content in a trophic level: Number of
organisms × dry mean mass of 1 organism ×
energy content of 1g of dry mass
Productivity: the rate which energy
passes through each trophic level
(kilojoules of energy per m2/year)
Primary Productivity (mj/m2/year): the amount
of energy fixed by photosynthesis
Less than 1% if sunlight energy is reaching the
earth is used for photosynthesis. Some light
absorbed will also be lost as respiratory heat
The rest are reflected by the earth’s surface,
used to heat the atmosphere, evaporate water.
Also different wavelengths of light may not be
captured by chlorophyll
Gross Primary Productivity: the rate at which
plants convert light energy into chemical energy.
The energy is lost between converting light
energy into chemical energy and so less energy
is left for primary consumers. The remaining
energy is called Net Primary Productivity
(kg/ha/year). This tells us how much energy is
available to heterotrophs.
Secondary Productivity
Primary consumers don’t always use up 100% of the plants
biomass because: some plants don’t die, consumers are
unable to consume the whole plant and most of the energy
that is absorbed is used to keep the organism alive rather
than to aid its growth
How to increase productivity
Primary Productivity
Planted earlier to provide a longer growing
season when there’s more sunlight
Grow in light banks
Irrigating crops
GM crops that are drought resistant/ mores
responsive to fertiliser/ pest- resistant
Grow in greenhouse to generate heat
Crop rotation to increase the amount of
nutrients available in the soil
Plant lots of nitrogen fixing crops around the
crops to replenish the nitrate levels
Use pesticides to remove pests and increase
the yield
Herbicides to kill weeds and reduce
competition
Fungicides: Fungi can cause fungal rot,
damage to xylem/ phloem tubes
Secondary Productivity
Harvesting animals just before adulthood
when the young animal is using most of its
energy in growth
Steroids (no longer used in the UK)
Selective breeding
Animals treated with antibiotics so that
less energy is used to treat infections
Reduce the animals movements as
much as possible
Maintain the optimal
temperature for them
Succession: is the directional
change in a community of organisms
over time
Sere: distinct stages with the non-
living environment becoming less
hostile
Pioneering Species: starts succession and can
begin on many different substrates.
1. Algae and lichens are the first to live on the
bare rock: this is the pioneering community.
These plants are resistant against salty water,
unstable sand and strong winds
2. The algae erodes through the rock and
when it dies, the rot produces soil for larger
plants to grow.
3. The wind blows the sand and a sand dune is
created. The roots of any vegetation here hold
the sand together to stabilise it. For example,
marram grass helps make the area more
stable by catching and trapping sand.
4. The increased stability helps other plants
grow and allows nutrients to be accumulated
5. Moss and ferns develop and when they
die, even larger plants succeed them. These
are called: Climax Community.
6. Other plants such as nitrogen fixing
bacteria grow and this helps increase the
concentration of nitrates in soil
Diversity
Key Words
Reliable: if the study were
repeated, would it produce
very similar results
Representative: gives a
good overall picture of
the variables you are
measuring
Unbiased: no human
influences on the results
Types of
sampling
Random Sampling: a random
coordinate generator is used
Stratified Sampling: used when
there’s multiple areas with
contrasting conditions
Systematic Sampling: when
samples are taken over a
transect
Line transects (observing
what species is found at 1
point touching the tape)
Belt transects (the quadrat is
placed at certain points along
the tape)
Methods
Density: counting the number of individuals
Percentage cover: estimate what proportion of
your quadrat is covered by your species
Biomass: collect, dry and weigh all the living
matters of your chosen organism from within your
quadrat
Relative Abundance: choose a category to describe
the abundance: (Abundant, common, frequent,
occasional, rare)
Percentage frequency: using a quadrat or point
(does the organism touch the corner of each box.
Each touch equates to 1%)
Calculations
Species Abundance: the number of individuals in each species
Species Richness: the number of different species
Species Diversity: takes both abundance and richness into account
Simpson’s Diversity Index
Population Size
K- strategist and
R- Strategist
K-Strategist: species whose
population is determined by
the carrying capacity. The
population tends to have a
low reproductive rate and
have slow growth. Tend to be
large
The limiting factor exerts a bigger effect
on the population as the population is
very close to the carrying capacity
R-strategist (the “boom
and bust” pattern): the
population size increases
so rapidly that it exceeds
the carrying capacity of the
habitat before limiting
factors start to have an
effect. Tend to be small
Once the carrying capacity has been
exceeded, there’s no longer enough
resources ot support all the
individuals and this leads to the
DEATH PHASE.
Growth Curve
Carrying capacity: is the maximum population size that can be
maintained over a period of time in a particular habitat
1. Lag phase: there are only a few individuals in the population and they
are still acclimatising. The rate of reproduction at this stage is low
2. Log phase: resources are plentiful and the conditions are advantageous.
This means the rate of reproduction is fast and exceeds the mortality rate.
3. Stationary phase: the population size levels out at the carrying capacity of
the habitat. The habitat cannot support a larger population. There might still
be small fluctuations. The rate of reproduction and mortality are equal
Predators and Prey
1. Large population of predators means more prey are eaten
2. The number of prey decrease= less food for predators
3. Fewer predators= the prey population can recover and increase
4. The prey population increases= more predators
Cycle repeats
Competition happens when there’s a
lack of resources available to support
all of the individuals present
Intraspecific competition: occurs between
individuals of the same species
Interspecific competition: occurs between
individuals of different species
More overlap between 2 species’
niches would result in more intense
competition
Competitive Exclusion Principle: if 2
species have the same niche, one
would be outcompeted by the other
and this would result in extinction
Allelopathy: is a form of competition because it
stops neighbouring organisms from using resources
in the habitat
An organism releases a chemical and
this chemical inhibits growth,
germination or nutrient uptake
Black Walnut Trees: releases
JUGLONE, which inhibits respiration in
neighbouring plants. This gives young
walnut trees better access to light
Sorghum: releases sorgolene
through its roots and prevents
respiration in neighbouring plants.
Sustainable Growth
Small Scale Timber Production
Coppicing: cutting a tree trunk close to the base to encourage
new growth.
1. Cut the DECIDUOUS TREES (the ones that shed leaves)
2. Lots of new shoots grow from the cut surface.
3. The narrow branches can be used in fencing, firewood
or furniture
4. The branches are cut and new shoots regrow
This can sometimes be done as Rotational Coppicing which is when the
woodland is divided into 2 and only 1 half is harvested to allow the other half to
grow. This is more sustainable and encourages biodiversity. If the woods were
left, it is hoped that it would return to normal
Some trees are left to grow without being coppiced. They are called standards
and provide larger pieces of timber
Pollarding: This is similar to coppicing but the tree
trunks are cut a little higher up to prevent deer and
other wildlife from feeding off the emerging shoots.
Large Scale Timber production
Clear felling: this destroys habitats on a large scale
and involves cutting all the trees in an area
This reduces soil mineral levels and makes it
more susceptible to flooding, erosion
The soil could also contaminate rivers
Sometimes, the area is clear felled but then left to mature for 50-100 years before
felling again to allow the biodiversity to increase
Modern sustainability forestry encourages that: the trees which are harvested
are then replaced by another tree. The woodland must also maintain its
ecological function and the local people should benefit from the forest.
Only the largest and most valuable trees are removed
Management
Control pests/ pathogens/ poachers/ predators
Only plants trees that will grow well in that environment
Position trees/ animals with distance between them to reduce competition
Raise
carrying
capacity
Move organisms to other areas which they might be able to benefit more from
Vaccinate animals
Set up SSI, National Parks or ex situ zoos/ botanical gardens
Conservation: involves maintenance of
biodiversity between species, genentic
diversity within species, habitat and
ecosystem
Humans
Over exploitation of wild population for food/ commerce
Habitat disrupted or fragmented
Species introduced to the ecosystem by humans may
outcompete the native species
Reasons for Conservation
Food source: genetic diversity of wild stands could be used to
breed for disease/ drought resistance or improved yield
Medicinal drugs
Biological control agents
Pollinating crops
Maintaining water quality
Climate stability: global warming, preventing floods
Ecotourism
Galapagos
Information
50% of vertebrate species and 25% of plant species are endangered
Population has increased from 5000 residents and 4000 tourists to 28,000 residents and
100,000 tourists from 1980 to 2005
Forests of Scalesia trees and shrubs have almost been completely eradicated in Santa Cruz and San Cristobal
Habitat Destruction: increased
demand for resources
Limit tourists
Increase protected areas
Encourage emigration and prevent further immigration
Careful city planning to prevent habitats from being fragmented
Pollution: increased need for oil and
increased production of waste
NOTE: Oil spill in 2001 caused damage to marine and costal ecosystem
Create no float zones or divert the ships
Overconsumption: mainly of giant tortoises, sea cucumbers, sharks fin, fur and whales
No take zones/ restrictions on what can be hunted and when it can be hunted
Newly introduced species
vs. endemic species
Red Quinine Trees: is an invasive species on Santa Cruz. It outcometes the Cacaolillo Strub and the Scalesia trees. This has also caused the Galapagos Petrel to lose it's nesting site
The goat eats everything and outcompetes the giant tortoise. This increases soil erosion
Cats and dogs attack birds and nests. They would even prey upon land tortoises and marine
iguanas.