B4.2 Ecological niches

What is an ecological niche?

The role of an organism in an ecosystem, including biotic and abiotic factors. No two species can fill the same niche within a habitat.

What is the difference between niche and habitat?

Niche = role, Habitat = address

What factors does the niche of an organism include?

Abiotic: zones of tolerance

Biotic: food supply - autotrophic/heterotrophic, utilisation of other species/interaction

What is an obligate aerobe?

Constant oxygen needed e.g. plants, animals

What is an obligate anaerobe?

Cannot tolerate oxygen e.g. bacteria - clostridium, methanogens

What are facultative anaerobes?

Switch between aerobic and anaerobic e.g. yeast, WhaE. coli

What is photosynthesis?

Production of organic compounds in cells using light energy.

Which organisms is photosynthesis the mode of nutrition for?

Plants, eukaryotic algae, groups of photosynthetic prokaryotes e.g. cyanobacteria

What is the base of most food chains?

Photosynthesis

What are heterotrophs?

Cannot make their own food, must take from other organisms - all animals

What is holozoic nutrition?

A form of heterotrophic nutrition where an organism:

• Ingests food

• Internally digests food

• Absorbs and assimilates the nutrients from digested food

• Unwanted food is egested

What are the stages of holozoic nutrition?

1. Ingestion - taking food into body

2. Digestion - breaking down food

3. Absorption - moving food into cells

4. Assimilation - making food part of cell

5. Elimination - removing unused food

What is an exception of holozoic nutrition?

Spiders - use external digestion

What are mixotrophs?

Can act as autotrophs by carrying out photosynthesis and act as heterotrophs by feeding on other organisms

What organisms are mixotrophs?

Freshwater protists e.g. euglena

What are the two types of mixotrophs?

1. Obligate mixotrophs - require both autotrophic and heterotrophic modes of nutrition to survive

2. Facultative mixotrophs - switch between two modes of nutrition based on available resources

What are saprotophs?

Heterotrophs that obtain nutrients by external digestion of food

What organisms are saprotrophs?

Bacteria and fungi - secrete enzymes onto dead matter and absorb products

What is the role of saprotrophs?

Decomposers, recycling nutrients like nitrogen and carbon, essential for ecosystem stability

What is archaea?

One of the 3 domains of life - prokaryotes, found in a wide variety of environments, metabolically diverse

What forms of nutrition are in archaea?

• Phototrophic

• Chemotrophic

• Heterotrophic

How is phototrophic nutrition used in archaea?

Absorb light using pigments other than chlorophyll

How is chemotrophic nutrition used in archaea?

Oxidise inorganic compounds e.g. iron ions

How is heterotrophic nutrition used in archaea?

Use organic molecules from other organisms

What is the family Hominidae?

Family of the great apes, all tailless primates. Includes modern humans and all our recent ancestors

What are herbivores?

Eat predominantly plants. Herbivorous hominids have large flat teeth and strong jaws for grinding seeds.

What are omnivores?

Eat plants and animals. Mixture of sharp incisors for ripping through meat, and flat molars

How can scientists make predictions about the diet of extinct species?

By examining the anatomy of fossils and comparing them to the anatomy of living descendants

What are some adaptations of plants to prevent herbivores from consuming them?

• Physical structures e.g. thorns on blackberry bushes

• Sharp trichomes on stinging nettles containing irritating chemicals

• Grass - tough fibrous leaves, cell walls containing silica

• Chilli plants - capsaicin (burning sensation)

• Tobacco - nicotine (toxin)

What are some adaptations of grazing mammals so that they can eat grass?

• Flat molars for grinding

• Teeth continue to grow throughout life so they are not worn down

What are some adaptations of insects to consuming plants?

• Chewing mouthparts

• Sharp mandibles with serrated edges to cut through the cell walls in leaves of plants

• Strong muscles to manipulate the mandibles to bite and grind leaves

What are some physical adaptions of predators?

• Sharp claws and talons to grip and hold onto prey

• Powerful jaws and teeth to capture and kill prey

• Speed and agility to chase and catch their prey

• Camouflage to blend in the environment

What are some chemical adaptions of predators?

• Production of venom which immobilises or kills prey

What are some behavioural adaptions of predators?

• Hunting in a pack to overwhelm large prey

• Ambush tactics

What are some physical adaptions of prey?

• Armour or protective covering to make it more difficult to kill the prey animal

• Swift and agile to outrun and avoid predators

• Camouflage to blend into the environment

• Mimicry of poisonous/unpalatable animals to avoid detection by predators

What are some chemical adaptions of prey?

• Toxic or unpalatable chemicals to discourage predators from eating them

• Bright colours and patterns to warn predators that they are toxic

What are some behavioural adaptions of prey?

• Travelling in groups to provide protection for individual animals against predators

• Moving in a swarm to confuse predators

• Alarm calls that alert others to the presence of a predator

• Nocturnality - adapt when they are active to avoid the times when predators are active

What are some plant adaptations for harvesting light?

• Trees that reach the canopy

• Epiphytes growing on branches of trees

• Shade-tolerant shrubs and herbs growing on the forest floor

What are some adaptations of canopy trees for harvesting light?

• Height and crown structure - tall trunks to reach sunlight, broad crowns to maximise absorption of light

• Broad, flat leaves to maximise absorption of light

What are some adaptations of lianas for harvesting light?

• Climb trunks of canopy trees to reach the light

• Rapid growth of stems and leaves to quickly reach the sunlight

• Flexible and thin stems to grow around obstacles and towards the light

• Large broad leaves to maximise light absorption for photosynthesis

What are some adaptations of epiphytes for harvesting light?

• Growing on canopy trees to harvest light that filters through the canopy

• Broad flat leaves that maximise surface area for light absorption

• Flexible growth, adjust towards the light

What are strangler epiphytes?

• Germinate in the branches of canopy trees and send aerial roots downwards to the forest floor

• Eventually surrounds trunk of the host tree and outcompetes it for light

• Gains access to the canopy by strangling the host tree

What are some adaptations of shade tolerant plants?

• Branching - increase surface area for absorbing light

• Broad leaves - maximise absorption of available light

• High concentration of chlorophyll to capture more of the available light

What is a fundamental niche?

Niche that an organism could potentially occupy in the absence of competition from other species. Determined by adaptations to the environment and zones of tolerance

What is a realised niche?

Niche that an organism does occupy due to competition from other species

What is the principle of competitive exclusion?

• Two species cannot coexist if niches overlap completely

• Less well adapted species will either be eliminated or restricted to a part of the niche

What does competitive exclusion explain?

Niche uniqueness in ecosystems