5. On the wild side
5.a Ecosystems and photosynthesis
Abundance and distribution
Key words
● Ecosystems - all abiotic and biotic factors in a particular area
● Habitat - place where an organism lives
● Population - all organisms of one species in a particular area
● Community - all interacting organisms in a particular area
● Abiotic factors - nonliving features (e.g. temperature)
● Biotic factors - living features (e.g. predators)
● Abundance - number of individuals of one species in a particular area
● Distribution - where a species is within a particular area
Abundance
● Abundance varies with a range of abiotic factors
1. Light intensity
2. Water availability
3. Temperature
4. Soil composition
● E.g. when the temperature is optimal for metabolic reactions, less energy is used
through thermoregulation meaning more is available for growth and reproduction -
population size/abundance will increase
● Abundance also varies with a range of biotic factors
1. Interspecific competition
2. Intraspecific competition
3. Predation
Competition and abundance
1. Interspecific competition
● When organisms of different species compete for the same resources
● This means resources are reduced
● Less food means less energy so less growth and reproduction therefore
population sizes will be reduced
2. Intraspecific competition
● When organisms of the same species compete for the same resources
● The population will grow when resources are plentiful
● However, eventually resources will become limited and the population size
will begin to decline
● With a smaller population, resources will increase
● The maximum stable population size that an ecosystem can support is called
the carrying capacity
3. Predation
● When an organism kills and eats another organism (predator and prey)
● As the prey population increases, so does the predators
, 5. On the wild side
● As predators increases, the prey population will begin to fall
● Less food for predators, so their population decreases
Niche
● A niche is the role the species play within its habitat
● Every species has its own unique niche
Succession
Succession is the process by which an ecosystem changes overtime
1. Primary succession
● Newly formed or exposed land
● No soil or organic material
2. Secondary succession
● Land that’s been cleared of all plants but soil remains
Primary succession
1. Pioneer species colonise the rocks, grow and release minerals
2. The pioneer species dies, decomposition forms thin layer of soil called humus
3. Other species such as mosses can now grow
4. Larger plants can grow as the soil deepens, larger plants die and soil continues to
deepen
5. Competition occurs, diversity increases
6. The area eventually reaches the climax community
Photosynthesis
Chloroplasts
● Double membrane called the chloroplast envelope which keeps reactants for
photosynthesis close to the reaction sites
● Thylakoid membranes to increase surface area allowing more light energy to be
absorbed, contain lots of ATP synthase
● Thylakoids are stacked to form grana which are joined by lamellae
● Photosynthetic pigments - chlorophyll a, chlorophyll b, carotene - which absorb the
light, attached to proteins to form photosynthesis
● PSI absorbs 700 nm wavelength light
● PSII absorbs 680 nm wavelengths
● Stroma containing enzymes, sugars and organic acids needed for photosynthesis
5.a Ecosystems and photosynthesis
Abundance and distribution
Key words
● Ecosystems - all abiotic and biotic factors in a particular area
● Habitat - place where an organism lives
● Population - all organisms of one species in a particular area
● Community - all interacting organisms in a particular area
● Abiotic factors - nonliving features (e.g. temperature)
● Biotic factors - living features (e.g. predators)
● Abundance - number of individuals of one species in a particular area
● Distribution - where a species is within a particular area
Abundance
● Abundance varies with a range of abiotic factors
1. Light intensity
2. Water availability
3. Temperature
4. Soil composition
● E.g. when the temperature is optimal for metabolic reactions, less energy is used
through thermoregulation meaning more is available for growth and reproduction -
population size/abundance will increase
● Abundance also varies with a range of biotic factors
1. Interspecific competition
2. Intraspecific competition
3. Predation
Competition and abundance
1. Interspecific competition
● When organisms of different species compete for the same resources
● This means resources are reduced
● Less food means less energy so less growth and reproduction therefore
population sizes will be reduced
2. Intraspecific competition
● When organisms of the same species compete for the same resources
● The population will grow when resources are plentiful
● However, eventually resources will become limited and the population size
will begin to decline
● With a smaller population, resources will increase
● The maximum stable population size that an ecosystem can support is called
the carrying capacity
3. Predation
● When an organism kills and eats another organism (predator and prey)
● As the prey population increases, so does the predators
, 5. On the wild side
● As predators increases, the prey population will begin to fall
● Less food for predators, so their population decreases
Niche
● A niche is the role the species play within its habitat
● Every species has its own unique niche
Succession
Succession is the process by which an ecosystem changes overtime
1. Primary succession
● Newly formed or exposed land
● No soil or organic material
2. Secondary succession
● Land that’s been cleared of all plants but soil remains
Primary succession
1. Pioneer species colonise the rocks, grow and release minerals
2. The pioneer species dies, decomposition forms thin layer of soil called humus
3. Other species such as mosses can now grow
4. Larger plants can grow as the soil deepens, larger plants die and soil continues to
deepen
5. Competition occurs, diversity increases
6. The area eventually reaches the climax community
Photosynthesis
Chloroplasts
● Double membrane called the chloroplast envelope which keeps reactants for
photosynthesis close to the reaction sites
● Thylakoid membranes to increase surface area allowing more light energy to be
absorbed, contain lots of ATP synthase
● Thylakoids are stacked to form grana which are joined by lamellae
● Photosynthetic pigments - chlorophyll a, chlorophyll b, carotene - which absorb the
light, attached to proteins to form photosynthesis
● PSI absorbs 700 nm wavelength light
● PSII absorbs 680 nm wavelengths
● Stroma containing enzymes, sugars and organic acids needed for photosynthesis
