4- ECOLOGY
Species and ecology terms
● Species → group of organisms that can interbreed and produce fer le, viable o spring.
● Popula on → group of organisms of the same species that live in the same area at the same
me.
● Community → di erent popula ons living and interac ng in the same area.
● Habitat → the environment in which a species lives.
● Ecosystem → community + environment (bio c and abio c factors).
Modes of nutri on
● Two methods of nutri on: autotrophs and heterotrophs.
AUTOTROPHS
● They synthesise organic molecules from inorganic nutrients: light and oxida on reac ons.
● Phototrophs → from light.
● Chemotrophs → from redox reac ons.
HETEROTROPHS
● They obtain their organic molecules from other organisms through feeding.
● Consumers ingest other organisms
● Detri vores ingest detritus (e.g. faeces)
● Saprotrophs externally digest dead organisms (decomposers)
Nutrient cycling
● Nutrients → materials required by organisms to survive.
● The environment’s supply of inorganic nutrients is limited, so these are recycled in 3 steps:
1. Autotrophs convert inorganic nutrients into organic molecules.
2. Heterotrophs ingest these organic molecules and produce inorganic byproducts.
3. Saprotrophs decompose dead organisms, returning the nutrients to the soil.
4. The cycle repeats.
Mesocosms
● Ecosystems describe the interac on between organisms and their environment.
● These can be sustainable over long periods of me as long as three condi ons are met:
1. Energy availability
2. Nutrient availability
3. Waste recycling
● Mesocosms → enclosed environments with controlled condi ons (e.g. terrariums).
● These can be used to study sustainability.
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, Species associa ons
● Can be either posi ve or nega ve, depending on the interac on between species in a habitat.
POSITIVE
● Species are found in the same habitat
● Can suggest two rela onships:
1. Predator-prey rela onship
2. Symbio c interac ons: mutualism, commensalism, parasi sm
NEGATIVE
● Species are not found in the same habitat
● Suggests compe on: niche par oning or compe ve exclusion
Quadrat sampling
● Used to iden fy the presence of two species within a given environment.
● Quadrat → a rectangular frame of known dimension.
● A quadrat is placed inside a speci c area and the number of organisms of a given species are
counted.
● This allows to calculate the popula on density and es mate the percentage coverage a er
various trials.
● However, it is mostly used only for non-mo le organisms (sessile organisms).
Energy ow
● Light is the source of energy for almost all communi es, but some producers derive energy from
chemical processes.
● This light energy is converted into chemical energy through photosynthesis.
● Heterotrophs obtain energy by feeding, and this energy is released via cellular respira on.
● In feeding sequences, there are various trophic levels.
● Trophic level → refers to the posi on an organism occupies within a feeding sequence.
● The rst trophic level is always occupied by the producer (usually an autotroph), followed by the
primary consumer, secondary consumer, ter ary consumer, etc.
● These feeding sequences are called FOOD CHAINS, and the arrows indicate the direc on of the
energy transfer.
fi tifl ti tititi
titi ti ti titi
tifiti titi tititi ti ti ti titi ft
Species and ecology terms
● Species → group of organisms that can interbreed and produce fer le, viable o spring.
● Popula on → group of organisms of the same species that live in the same area at the same
me.
● Community → di erent popula ons living and interac ng in the same area.
● Habitat → the environment in which a species lives.
● Ecosystem → community + environment (bio c and abio c factors).
Modes of nutri on
● Two methods of nutri on: autotrophs and heterotrophs.
AUTOTROPHS
● They synthesise organic molecules from inorganic nutrients: light and oxida on reac ons.
● Phototrophs → from light.
● Chemotrophs → from redox reac ons.
HETEROTROPHS
● They obtain their organic molecules from other organisms through feeding.
● Consumers ingest other organisms
● Detri vores ingest detritus (e.g. faeces)
● Saprotrophs externally digest dead organisms (decomposers)
Nutrient cycling
● Nutrients → materials required by organisms to survive.
● The environment’s supply of inorganic nutrients is limited, so these are recycled in 3 steps:
1. Autotrophs convert inorganic nutrients into organic molecules.
2. Heterotrophs ingest these organic molecules and produce inorganic byproducts.
3. Saprotrophs decompose dead organisms, returning the nutrients to the soil.
4. The cycle repeats.
Mesocosms
● Ecosystems describe the interac on between organisms and their environment.
● These can be sustainable over long periods of me as long as three condi ons are met:
1. Energy availability
2. Nutrient availability
3. Waste recycling
● Mesocosms → enclosed environments with controlled condi ons (e.g. terrariums).
● These can be used to study sustainability.
ti ti ti ti ff ti tititi titi ti ti ti ti ti ti ff ti
, Species associa ons
● Can be either posi ve or nega ve, depending on the interac on between species in a habitat.
POSITIVE
● Species are found in the same habitat
● Can suggest two rela onships:
1. Predator-prey rela onship
2. Symbio c interac ons: mutualism, commensalism, parasi sm
NEGATIVE
● Species are not found in the same habitat
● Suggests compe on: niche par oning or compe ve exclusion
Quadrat sampling
● Used to iden fy the presence of two species within a given environment.
● Quadrat → a rectangular frame of known dimension.
● A quadrat is placed inside a speci c area and the number of organisms of a given species are
counted.
● This allows to calculate the popula on density and es mate the percentage coverage a er
various trials.
● However, it is mostly used only for non-mo le organisms (sessile organisms).
Energy ow
● Light is the source of energy for almost all communi es, but some producers derive energy from
chemical processes.
● This light energy is converted into chemical energy through photosynthesis.
● Heterotrophs obtain energy by feeding, and this energy is released via cellular respira on.
● In feeding sequences, there are various trophic levels.
● Trophic level → refers to the posi on an organism occupies within a feeding sequence.
● The rst trophic level is always occupied by the producer (usually an autotroph), followed by the
primary consumer, secondary consumer, ter ary consumer, etc.
● These feeding sequences are called FOOD CHAINS, and the arrows indicate the direc on of the
energy transfer.
fi tifl ti tititi
titi ti ti titi
tifiti titi tititi ti ti ti titi ft
