Habitat
Place where an organism lives
Features of a habitat
Provides and organism with all the resources it needs to survive and reproduce
Describe a habitat (3)
Geographical location
Physical location
Type of ecosystem
Geographical location
Where habitat is found
May refer to the localised region of the habitat
Geographical location examples (3)
Latitude
Longitude
Climate
Physical location
Characteristics of geographical area where the habitat is found
Physical location examples (4)
Landforms
Water bodies
Vegetation
Microhabitats
Ecosystem
Location where a community of organisms interact with each other and with the abiotic environment
Biotic factors affect communities (4)
Availability of food
Amount of food increase → more food to feed animals → More likely to survive & reproduce → Population increase
Reverse happens for increase amount of food
Number of predators
No. of predators increase → More prey is consumed → Population decrease
Reverse for decrease in no. of predators
New pathogens
New pathogen → Population has no resistance → Wipe out quickly
Competition
One species is more adapted to environment than others → Outcompete till number of lesser adapted species are insufficient to breed
Organisms compete with other species / same species for resources
Abiotic factors affect communities (2) [1.→4] [2.→2]
Environmental conditions
Temperature
Affect rate of photosynthesis
Light intensity
Light is needed for photosynthesis
Rate of photosynthesis affects rate of plant growth
Plants are food sources / shelters for many organisms
Moisture
Plants & animals need water to survive
Soil pH & Mineral content
Soil pH affect affect rate of decay & how fast mineral ions return to soil
Diff species of plants thrive on diff nutrient conc. levels
Toxic chemicals
Fertiliser - Eutrophication
Pesticide build up in food chains - Bioaccumulation
Adaptations of organisms to abiotic challenges within its habitat [marram grass in sand dunes]
Leaves roll into tube w/ stomata inside
Trap moist air inside
Maintain high humidity outside stomata & reduce rate of transpiration
Stomata has hair & is found in sunken pits
Traps moist air outside stomata
Reduce rate of transpiration
Leaves have thick waxy cuticle
Reduce evaporation of water from leaves
Long roots that reach deep into sand for water
Extensive roots near surface → Helps sand retain water
Xerophyte
Thrives in dry conditions where most plants would curl up and die
Adaptations of organisms to abiotic challenges within its habitat
Red mangrove tree in mangrove swamp [unstable soil]
Prop roots from trunks for stability
Widespread & shallow root system for additional support
Adaptations of organisms to abiotic challenges within its habitat
Red mangrove tree in mangrove swamp [anoxic soil]
Aerial roots [pneumatophores] grow above soil
Low tide - Gas exchange happen through open passages
Air transported to parts of underground roots
Adaptations of organisms to abiotic challenges within its habitat
Red mangrove tree in mangrove swamp [salt water] (1)
Salt filtration
Plasma membrane stops salt from entering cytoplasm while letting water in
Seeds start germinating before falling from tree
Adaptations of plants in hot deserts (5)
Succulence
Many desert plants have fleshy stems & leaves for water storage
Reduced leaf SA
Reduced SA reduces water loss via transpiration
Deep root system
Allow desert plants to access groundwater
Widespread root systems near surface to collect rainfall
CAM physiology [Type of photosynthesis]
Stomata closes during the day [reduce water loss via transpiration]
Stomata opens at night when its cooler
Thick waxy cuticles
Reduce water loss via evaporation from plant
Adaptations of plants in deserts [saguaro cactus] (5)
Succulence
Fleshy stems & leaves for water storage
Water storage tissues - survive w/o rain
Spines
Reduce leaf SA for transpiration
Protection from predators
Widespread root system → Allow absorption of any available water
Water storage tissues allow cacti to survive w/o rainfall for a long time
Thick waxy cuticle → Prevent water loss
Adaptations of animals in hot deserts (4)
Nocturnal behaviour
Active at night [cooler → reduce water loss]
Burrow underground during hottest part of the day
Efficient water conservation
Produce concentrated urine
Many insects & birds produce uric acid instead of urine [reduce water loss]
Efficient metabolism
Metabolic adaptations allow them to cope w/ limited food sources [e.g. low metabolic rates / ability to store fat]
Camouflage
Avoid being seen by predators or prey
Adaptations of animals in deserts [camels] (7)
Efficient water conservation
Produce concentrated urine
Intestines extract lots of water from faeces
High temp tolerance → Reduce water loss from sweating
Long legs → Keep body above hot sand
Long nasal passages → Trap & reabsorb moisture from exhaled air
Broad feet → Efficiently walk over sandy terrain
Large SA : V → Efficient heat loss
Fat storage
Store fats in humps
Fats are metabolised to make energy and water when scarce
Species
Group of organisms capable of reproducing with each other to produce fertile offspring
Unable to produce fertile offspring with diff species
When 2 species produce offspring by cross-breeding, hybrids are reproductively sterile
Population
All the organisms of a specific species in a habitat
Natality
Birth rate
Mortality
Death rate
Immigration
New individuals entering a population
Emmigration
Individuals leaving a population
Change in population size equation
(Natality + Immigration) - (Mortality + Emigration)
(N + I) - (M + E)
Intraspecific competition
Competition for resources between members of the same species
Community
All the different species in a habitat
Formed by populations of different species living & interacting with each other in a habitat
Interactions between species examples (5)
Predator & prey
Herbivory
Competition for resources
Mutualism
Parasitism
Factors that affect coral reef formation (5)
Water clarity
Water depth
Temperature
pH
Salinity
How does water clarity affect coral reef formation
Less light
Less photosynthesis
Less growth
How does water depth affect coral reef formation
Deeper → Less light reaches coral reef
Less photosynthesis
Less growth
How does temperature affect coral reef formation
Higher temp causes coral bleaching
Narrow range of tolerance
High temp → Enzymes denature → Less successful collisions → Less growth
Low temp kills corals
How does pH affect coral reef formation
Narrow range
Ocean acidification
CO2 dissolve into water to form carbonic acid
Threat to coral reef
How does salinity affect coral reef formation
Narrow range 23-42 g/kg
Average : 35 g/kg
Optimum range of tolerance [Shelford’s Law of Tolerance]
16-34
Reproductive isolation
When there’s a barrier which prevents individuals from reproducing
Competitive exclusion
If 2 species occupy the same niche, there will be an inferior competitor that goes extinct
Niche
The role of a species in an ecosystem
Niche partitioning
For 2 species with similar niches
The coexistence of 2 species due to small differences in their niches
Fundamental niche
Potential niche of a species based on adaptations & tolerance limits
Realised niche
Actual niche of a species when in competition with other species
Obligate anaerobe
Organism that must live in an environment without oxygen
Obligate aerobe
Organism that must live in an environment with oxygen
Facultative anaerobe
Organism that can live in environments with or without oxygen
Autotrophs
Organism that produce carbon compounds from inorganic compounds using light / inorganic chemical energy
Heterotrophs
Organism that obtains carbon compounds from other organic sources
Saprotrophs
Heterotrophs but not consumers
Secretes enzymes to external environment & digests food externally
Absorbs only digested nutrients
Holozoic
Obtain nutrition by ingesting food, digesting internally, absorbing it, & assimilating it
Mixotrophs
Organism that is capable of both photosynthesis & heterotrophy
Autotroph + Heterotroph
Obligate mixotroph
Must use both photosynthesis & heterotrophy
Facultative mixotroph
Can use either photosynthesis or heterotrophy
Archaea
Single celled organisms
Unique from Eukaryota & Bacteria
Can thrive in extreme environmental conditions
[e.g. hot springs, salt lakes, etc]
Diverse groups [some are phototrophs, some are chemotrophs]
Biodiversity
Variety of living organisms in an ecosystem
Why is high biodiversity important
Makes sure that ecosystems are stable
Different species depend on each other [shelter, food]
Different species maintain the right physical environment
Trophic levels (5)
Producer
Primary consumer [herbivore / omnivore]
Secondary consumer [omnivore / carnivore]
Tertiary consumer [top carnivore]
Decomposer
Food chains
Show whats eaten by what in an ecosystem
Food webs
Show how food chains are linked
Pyramid of numbers
Each bar shows number of organisms at each stage of the food chain
Goes up by the food chain
Doesn’t have to look like a pyramid
Biomass
Dry mass
Pyramid of biomass
Each bar shows mass of living material at each stage of food chain
Goes up by food chain
Look like a pyramid most of the time
Pyramid of energy transfer
Shows the energy transferred to each trophic level in a food chain
Always look like a pyramid
How is energy transferred along the food chain
Sun provides energy to organisms
Plants use energy from sun to make food during photosynthesis
Not all energy is transferred (4)
Some parts of food is not eaten [bones, roots]
Energy isn’t taken in
Some parts of food is indigestible [e.g. fibre]
Passed out as waste [faeces]
Glucose / energy used in respiration
Energy transferred to surroundings as heat
Equation for efficiency of biomass transfer
(Biomass transferred to next level / Biomass available at the previous level) x 100
Carbon cycle (combustion) (5)
Green plants & algae take in CO2 from atmosphere during photosynthesis
CO2 locked up in biological molecules
Plants / animals are used to make products
Un-decayed organic material becomes fossil fuel
Products are burnt
Fossil fuel burnt for energy
CO2 is produced & released into air
Carbon cycle (animal respiration) (5)
Green plants & algae take in CO2 from atmosphere during photosynthesis
CO2 in plants locked up in biological molecules
Passed to animals who eat the plants
CO2 in animals locked up in biological molecules
Animals respire to release CO2
Carbon cycle (plant respiration) (3)
Green plants & algae take in CO2 from atmosphere during photosynthesis
CO2 in plants locked up in biological molecules
Plants respire to release CO2
Carbon cycle (decomposition) (6)
Green plants & algae take in CO2 from atmosphere during photosynthesis
CO2 in plants locked up in biological molecules
Passed to animals who eat the plants
CO2 in animals locked up in biological molecules
Animals excrete waste / die
Waste decay → CO2 released from decay into air
Carbon sink
Absorbs more carbon than it releases
Ecosystems where photosynthesis exceeds respiration
Carbon source
Releases more carbon than it absorbs
Ecosystems where respiration exceeds photosynthesis
Nitrogen fixation
Turning N2 from the air into nitrogen compounds in the soil which plants can use
Decomposers
Break down proteins [in rotting plants & animals] & urea [animal waste] and turn them into ammonia [nitrogen compound]
Forms ammonium ions in soil
Nitrifying bacteria
Nitrification
Turn ammonium ions in decaying matter into nitrates
Nitrogen-fixing bacteria
Turn N2 in air into nitrogen compounds for plants to use
Denitrifying bacteria
Turn nitrates back into N2 gas
Nitrogen cycle (decompose) (6)
Nitrogen fixing bacteria in roots turn N2 in air into plant protein
Plants are eaten by animals → Nitrogen passed to animals
Animals die / produce waste
Animals / waste decompose into ammonia
Nitrifying bacteria turn ammonia into nitrates in soil
Denitrifying bacteria turns nitrates into N2 in air
Nitrogen cycle (lightning) (2)
Energy from lightning allows nitrogen to react with oxygen in air to give nitrates
Denitrifying bacteria turn nitrates in soil back into N2 in air
Nitrogen cycle (air) (2)
Nitrogen fixing bacteria turns N2 in air into nitrates
Denitrifying bacteria turn nitrates in soil back into N2 in air
Water cycle (6)
Sun provide energy
Water from lakes, rivers, oceans, puddles, soil, leaves evaporate
Water condenses into clouds [can be blown from one region to another]
Water fall back down to earth as liquid water in the form of rain [precipitation]
Water seeps into soil
Water flows into rivers
Water taken up by plants
Repeat