06. Ecology

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)

1. Geographical location

2. Physical location

3. Type of ecosystem

Geographical location

• Where habitat is found

• May refer to the localised region of the habitat

Geographical location examples (3)

1. Latitude

2. Longitude

3. Climate

Physical location

Characteristics of geographical area where the habitat is found

Physical location examples (4)

1. Landforms

2. Water bodies

3. Vegetation

4. Microhabitats

Ecosystem

Location where a community of organisms interact with each other and with the abiotic environment

Biotic factors affect communities

1. 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

2. Number of predators

   • No. of predators increase → More prey is consumed → Population decrease

   • Reverse for decrease in no. of predators

3. New pathogens

   • New pathogen → Population has no resistance → Wipe out quickly

4. 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

1. 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

2. Toxic chemicals

   • Fertiliser - Eutrophication

   • Pesticide build up in food chains - Bioaccumulation

Adaptations of organisms to abiotic challenges within its habitat Examples

Marram grass in sand dunes

1. Leaves roll into tube w/ stomata inside

   • Trap moist air inside

   • Maintain high humidity outside stomata & reduce rate of transpiration

2. Stomata has hair & is found in sunken pits

   • Traps moist air outside stomata

   • Reduce rate of transpiration

3. Leaves have thick waxy cuticle

   • Reduce evaporation of water from leaves

4. Long roots that reach deep into sand for water

5. Extensive roots near surface → Helps sand retain water

Red mangrove tree in mangrove swamp

• Unstable soil

  • Prop roots from trunks for stability

  • Widespread & shallow root system for additional support

• Anoxic soil

  • Aerial roots [pneumatophores] grow above soil

    • Low tide - Gas exchange happen through open passages

    • Air transported to parts of underground roots

• High salinity water

  • Salt filtration

    • Plasma membrane stops salt from entering cytoplasm while letting water in

  • Seeds start germinating before falling from tree

Xerophyte

Thrives in dry conditions where most plants would curl up and die

Adaptations of plants in hot deserts

1. Succulence

   • Many desert plants have fleshy stems & leaves for water storage

2. Reduced leaf SA

   • Reduced SA reduces water loss via transpiration

3. Deep root system

   • Allow desert plants to access groundwater

   • Widespread root systems near surface to collect rainfall

4. CAM physiology [Type of photosynthesis]

   • Stomata closes during the day [reduce water loss via transpiration]
     Stomata opens at night when its cooler

5. Thick waxy cuticles

   • Reduce water loss via evaporation from plant

Adaptations of plants in deserts Example

• Saguaro cactus

  1. Succulence

     • Fleshy stems & leaves for water storage

     • Water storage tissues - survive w/o rain

  2. Spines

     • Reduce leaf SA for transpiration

     • Protection from predators

  3. Widespread root system

     • Allow absorption of any available water

  4. Water storage tissues

     • Allow cacti to survive w/o rainfall for a long time

  5. Thick waxy cuticle

     • Prevent water loss

Adaptations of animals in hot deserts

1. Nocturnal behaviour

   • Active at night [cooler → reduce water loss]

   • Burrow underground during hottest part of the day

2. Efficient water conservation

   • Produce concentrated urine

   • Many insects & birds produce uric acid instead of urine [reduce water loss]

3. Efficient metabolism

   • Metabolic adaptations allow them to cope w/ limited food sources [e.g. low metabolic rates / ability to store fat]

4. Camouflage

   • Avoid being seen by predators or prey

Adaptations of animals in deserts Example

• Camels

  1. Efficient water conservation

     • Produce concentrated urine

     • Intestines extract lots of water from faeces

  2. High temp tolerance

     • Reduce water loss from sweating 

  3. Long legs

     • Keep body above hot sand

  4. Long nasal passages

     • Trap & reabsorb moisture from exhaled air

  5. Broad feet

     • Efficiently walk over sandy terrain

  6. Large SA : V

     • Efficient heat loss

  7. Fat storage

     • Store fats in humps

     • Fats are metabolised to make energy and water when scarce

Adaptations of plants in tropical rainforests

1. Buttress roots

   • Large overground roots that provide stability and absorb nutrients from the shallow topsoil

2. Drip tips

   • Leaves are elongated and have pointed ends

   • Allows water to run off quickly

   • Prevents water-logging and the growth of fungi

3. Uses available resources

   • Uses trees for support or grow on them to reach the canopy easier

4. Mutualistic relationships

   • Many plants have developed mutualistic relationships with animals for pollination and seed dispersal

Adaptations of plants in tropical rainforests Example

• Dipterocarp trees

  • Tall tree

    • Can access sunlight for photosynthesis as it reaches the canopy layer of the rainforest

  • Fast growth rate

    • Allows it to reach the canopy quickly

  • Buttress roots

    • Overground

    • Prevents the large tree from toppling

  • Large leaves

    • Maximise light absorption for photosynthesis

  • Large quantities of fruits

    • Increases the chance of reproductive success

    • Animals consume the fruit and help with seed dispersal

  • Chemical defences

    • Leaves contain toxins to deter insects from eating them

• Epiphytes

  • Grows on other trees and uses them for support

  • Obtain nutrients from the air and rain

• Lianas

  • Vines that grow up the trunks of tall trees to reach the light

Adaptations of animals in tropical rainforests

1. Arboreal adaptations

   • Allows the animal to live in the tree canopy

     • E.g. Prehensile tails, grasping hands & feet, strong limbs

2. Acute senses

   • High developed sense of sight, hearing, and smell

   • Allow them to navigate through the vegetation to locate food sources and predators

3. Camouflage

   • Help predators to ambush prey

   • Help prey to avoid predators

Adaptations of animals in tropical rainforests Example

• Sumatran orangutans

  • Long arms & grasping feet

    • Move from branch to branch in tree canopy

  • Opposable fingers & toes

    • Grasp tree branches & manipulate tools

  • Colour vision

    • Recognise edible fruits + predators

  • Camouflage

    • Reddish-brown hair blends into forest canopy

  • Intelligence

    • Can use tools to obtain food

  • Strong jaws & teeth

    • Eat unripe fruit

Factors that affect coral reef formation (5)

1. Water clarity

2. Water depth

3. Temperature

4. pH

5. Salinity

How does water clarity affect coral reef formation

• Less light

• 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 water depth affect coral reef formation

• Deeper → Less light reaches coral reef

• Less photosynthesis

• Less growth

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

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 one specific species in one location at a time

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)

Types of intraspecific interactions

• Intraspecific competition

• Intraspecific cooperation

Intraspecific competition

• Competition for resources between members of the same species

• Increases due to density dependent factors

• Influences population size

• Lead to territoriality & increased aggression within a species

Reasons of intraspecific competition

• Territory [for feeding & reproduction]

• Mates [for reproduction]

• Social dominance in social species

Examples of intraspecific competition

1. Territory

   • American robins

     • Males robins compete for territory for mating & raising young

     • Female robins select mates based on the quality of their nesting sites

   • Oak trees

     • Oak trees growing close together in a woodland will compete for light, water, and minerals

2. Mates

   • Southern elephant seals

     • Males fight for dominance over a harem of females

     • Dominant male has greater access to females for reproduction

   • Red deer

     • Male red deer fight with each other for access to females

     • Dominant male will mate with all of the females in the group

3. Social dominance

   • Chimpanzees

     • Compete with each other for social position [e.g. being the alpha male]

     • Higher social position have preferential access to food & mates

Intraspecific cooperation

• Members within a species work together to aid survival of a group

Types of intraspecific cooperation

• Group hunting

• Group foraging

• Defence against predators

• Parenting

Examples of intraspecific cooperation

1. Group hunting

   • Wolves

     • Hunt in packs

     • More likely for successful hunt

     • All members of the pack gain access to food

2. Group foraging

   • Bees

     • Cooperate to forage & collect nectar for their hive

     • Use a “waggle dance” to communicate with other workers when they find a good source of nectar

3. Defence against predators

   • Meerkats

     • Communicate danger from predators using alarm calls

     • Allows other meerkats to forage safely for food

4. Parenting

   • Orangutans

     • Females spend 9 yrs teaching their child what they need to survive

Types of interspecific interactions

1. Herbivory

2. Predation

3. Interspecific competition

4. Mutualism

5. Parasitism

6. Pathogenicity

Herbivory [interspecific interaction]

• Eating plants

• Affects plant growth, reproduction, and diversity

Examples of herbivory interactions [interspecific interaction]

• Red deers are herbivores that eat grass

• Cattle graze eat grass

• Sea turtles feed on sea grass

• Honeybees consume nectar & pollen

Predation [interspecific interaction]

• Predator hunts and feeds on prey

Examples of predation interaction [interspecific interaction]

• Dolphins catch and eat fish

• Lions hunt and eat zebras

• Red kites eat roadkill

Interspecific competition

• Competition for resources between members of a different species

• Can lead to competitive exclusion, niche differentiation, or coexistence

Examples of interspecific competition [interspecific interaction]

• Oak and beech trees compete for light and minerals

• Lions and hyenas compete for prey

• Red and grey squirrels compete for food and territory

Mutualism

• Organisms of different species working together for the benefit of both

Examples of mutualistic relationship

• Bees and dandelions

  • The bee benefits from source of food

  • Dandelions benefit from being pollinated

• Anemone and clownfish

  • Anemone protects clownfish

  • Clownfish provides faecal matter for food

• Root nodules and Fabaceae

  • Root nodules contain nitrogen-fixing bacteria

  • Provides fabaceae with a supply of nitrogen compounds

  • Nitrogen fixing bacteria in root nodules receive carbohydrates and other organic compounds produced through photosynthesis of the Fabaceae

• Mycorrhizae and Orchidaceae

  • Mycorrhizae provide larger SA for Orchidaceae to absorb water and minerals

  • Mycorrhizae enhances the Orchidaceae’s ability to acquire nutrients

  • Orchidaceae provides Mycorrhizae with carbohydrates and protection

• Corals and zooxanthellae

  • Corals provide zooxanthellae with a protected environment

  • Coral polyp cells produce CO₂ and water for the zooxanthellae to use for photosynthesis

  • Zooxanthellae uses photosynthesis to produce nutrients [e.g. glucose] which is used by corals

  • Zooxanthellae helps corals to remove wastes and produce oxygen

Parasitism

• When one species benefits from the harm of the other species

Examples of parasitic relationship

• Dogs and fleas

  • Fleas live by feeding on the blood of dogs or mammals in general

• Mistletoe plants and trees

  • Mistletoe plants grow in the branches of trees, taking water and nutrients from the host

Pathogenicity

• When an organism infects another species, causing a disease

Examples of pathogenic relationship

• Malarial parasite and humans

  • Malarial parasite enters the human bloodstream and causes malaria

• Mycobacterium tuberculosis bacteria and humans

  • Mycobacterium tuberculosis bacteria causes tuberculosis in humans

• Fungal pathogen and humans

  • Fungal pathogen causes dutch elm disease in elm trees which causes them to lose their leaves and die

Competitive exclusion

• No 2 species can occupy the same ecological niche in the same environment for a prolonged time

• If 2 species occupy the same niche, there will be an inferior competitor that goes extinct

Invasive species

• Organism that have been introduced to an ecosystem and do not ocur there naturally

• Causes harm to the natural ecosystem

Endemic species

Native species

Ways in which invasive species have better chance of survival in a habitat and replace endemic species [competitive exclusion]

1. Absence of predators

2. Absence of diseases

3. Faster rate of reproduction

4. Larger size / more aggressive

5. Outcompeting for food and resources

Example of competitive exclusion

• Red & Grey squirrel

  • Grey squirrels are larger & stronger

    • Outcompete red squirrels for food & habitat

  • Grey squirrels reproduce faster than red squirrels

  • Grey squirrels are immune to squirrel pox virus which kills the red squirrels

Community

• All the different species in a habitat

• Formed by populations of different species living & interacting with each other in a habitat

Reproductive isolation

When there’s a barrier which prevents individuals from reproducing

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)

1. Producer

2. Primary consumer [herbivore / omnivore]

3. Secondary consumer [omnivore / carnivore]

4. Tertiary consumer [top carnivore]

5. 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

1. Sun provides energy to organisms

2. Plants use energy from sun to make food during photosynthesis

Not all energy is transferred (4)

1. Some parts of food is not eaten [bones, roots]

   • Energy isn’t taken in

2. Some parts of food is indigestible [e.g. fibre]

   • Passed out as waste [faeces]

3. Glucose / energy used in respiration

4. 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)

1. Green plants & algae take in CO₂ from atmosphere during photosynthesis

2. CO₂ locked up in biological molecules

3. Plants / animals are used to make products
   Un-decayed organic material becomes fossil fuel

4. Products are burnt
   Fossil fuel burnt for energy

5. CO₂ is produced & released into air

Carbon cycle (animal respiration) (5)

1. Green plants & algae take in CO₂ from atmosphere during photosynthesis

2. CO₂ in plants locked up in biological molecules

3. Passed to animals who eat the plants

4. CO₂ in animals locked up in biological molecules

5. Animals respire to release CO₂

Carbon cycle (plant respiration) (3)

1. Green plants & algae take in CO₂ from atmosphere during photosynthesis

2. CO₂ in plants locked up in biological molecules

3. Plants respire to release CO₂

Carbon cycle (decomposition) (6)

1. Green plants & algae take in CO₂ from atmosphere during photosynthesis

2. CO₂ in plants locked up in biological molecules

3. Passed to animals who eat the plants

4. CO₂ in animals locked up in biological molecules

5. Animals excrete waste / die

6. 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)

1. Nitrogen fixing bacteria in roots turn N₂ in air into plant protein

2. Plants are eaten by animals → Nitrogen passed to animals

3. Animals die / produce waste

4. Animals / waste decompose into ammonia

5. Nitrifying bacteria turn ammonia into nitrates in soil

6. Denitrifying bacteria turns nitrates into N₂ in air