Predation (4.3)

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Define predation.

Predation is an interspecific interaction in which one organism (the predator) hunts, kills and eats another organism (the prey).

What is a predator?

A predator is an organism that hunts, captures, kills and consumes another living organism.

What is prey?

Prey is the organism that is hunted, captured and eaten by a predator.

Define predator-prey relationship.

A predator-prey relationship is an ecological interaction where a predator feeds on a prey organism, causing changes in the population sizes of both species.

Define competition.

Competition occurs when two or more organisms compete for the same limited resources such as food, water, shelter, light, nutrients or space.

Define ecological niche.

An ecological niche is the role of a species in an ecosystem, including how it uses resources and interacts with other organisms and the environment.

Define intraspecific competition.

Intraspecific competition is competition between individuals of the same species for limited resources.

Give an example of intraspecific competition.

Two male deer competing for mates.

Define interspecific competition.

Interspecific competition is competition between individuals of different species that use similar resources or occupy similar niches.

Give an example of interspecific competition.

A wolf and a lynx competing for snowshoe hares.

Define resource partitioning.

Resource partitioning is the process whereby species use the same resource in different ways, places or times, reducing competition and allowing coexistence.

Define coexistence.

Coexistence occurs when different species live in the same habitat without one species excluding the other.

What are population interactions (interspecific interactions)?

Population interactions are relationships between populations of different species living together that influence each other's survival, growth and reproduction.

What is mutualism?

Mutualism is an interaction in which both species benefit (+/+).

What is parasitism?

Parasitism is an interaction where the parasite benefits while the host is harmed (+/−).

What is commensalism?

Commensalism is an interaction where one species benefits and the other is unaffected (+/0).

What is amensalism?

Amensalism is an interaction where one species is harmed while the other remains unaffected (−/0).

State the effects on each species in mutualism.

Species A (+), Species B (+).

State the effects on each species in competition.

Species A (−), Species B (−).

State the effects on each species in predation.

Predator (+), Prey (−).

State the effects on each species in parasitism.

Parasite (+), Host (−).

State the effects on each species in commensalism.

One species (+), the other (0).

State the effects on each species in amensalism.

One species (−), the other (0).

Why are predators successful hunters?

They possess adaptations that improve their ability to locate, capture and kill prey.

List adaptations commonly found in predators.

Sharp teeth, Sharp claws, Excellent eyesight, Acute sense of smell, Speed, Agility, Camouflage, Powerful muscles.

Why is camouflage advantageous to predators?

It allows predators to approach prey without being detected.

Why have prey species evolved defence mechanisms?

To reduce the risk of being captured and eaten by predators.

What is camouflage (cryptic colouration)?

An adaptation that allows an organism to blend into its surroundings and avoid detection.

Give an example of camouflage.

A stick insect resembling a twig.

What is warning colouration (aposematism)?

Bright, conspicuous colours that warn predators that an organism is toxic, poisonous or unpalatable.

Give an example of warning colouration.

The orange and black colours of the Monarch butterfly.

What is chemical defence?

The production or storage of toxic substances that deter predators.

How does the Monarch butterfly obtain its chemical defence?

Its caterpillars feed on milkweed plants and accumulate toxic cardiac glycosides.

What is herding as a defence mechanism?

Living in groups to reduce the chance of an individual being captured by a predator.

Why is predation important in ecosystems?

Transfers energy between trophic levels, Controls prey populations, Maintains ecological balance, Promotes biodiversity, Prevents overpopulation.

How does predation contribute to energy flow?

It transfers energy fixed by producers to herbivores and then to carnivores.

Why would energy flow be disrupted without predation?

Energy stored in plant tissues would not efficiently move to higher trophic levels.

How do predators regulate prey populations?

By removing individuals from prey populations, preventing excessive population growth.

Why are predators considered population control agents?

They prevent prey populations from increasing beyond the carrying capacity of the ecosystem.

What could happen if predators were removed from an ecosystem?

Prey populations may increase rapidly. Resources may become depleted. Competition may increase. Biodiversity may decrease. Ecosystem stability may be lost.

What is meant by predator-prey dynamics?

The cyclical relationship between predator and prey population sizes over time.

Why do predator populations increase when prey populations increase?

More prey means more food is available for predators.

Why do prey populations decrease when predator populations increase?

More predators consume more prey.

Why do predator populations decrease after prey populations decline?

There is less food available.

Why do prey populations recover after predator populations decrease?

Reduced predation allows prey numbers to increase.

What type of factor is predation?

A density-dependent factor.

Why is predation considered density-dependent?

Its effect becomes stronger as prey population density increases.

Describe the typical pattern shown on a predator-prey graph.

Prey population rises first. Predator population rises shortly afterwards. Prey population decreases. Predator population decreases after a time lag. The cycle repeats.

Why is there a time lag between prey and predator peaks?

Predator populations need time to respond reproductively to increased food availability.

Which population peaks first on a predator-prey graph?

The prey population.

Which population peaks second on a predator-prey graph?

The predator population.

What happens if the prey population suddenly decreases?

The predator population decreases shortly afterwards.

What should you mention when interpreting a predator-prey graph in an exam?

Prey increase first. Predator increase follows after a lag. Increased predation causes prey decline. Reduced prey causes predator decline. Cycle repeats continuously.

What diagram must you be able to interpret for IEB examinations?

A predator-prey population graph showing cyclical fluctuations and a time lag between prey and predator populations.

How do predators promote biodiversity?

They prevent one prey species from becoming dominant and excluding others.

What happened when Pisaster starfish were removed from rocky shore ecosystems?

More than ten invertebrate species became extinct due to increased competition among prey species.

What ecological principle does the Pisaster example demonstrate?

Predators help maintain species diversity.

What is predator prudence?

The principle that predators generally do not eliminate all their prey because doing so would ultimately threaten their own survival.

Why is predator prudence important?

It promotes long-term survival of both predator and prey populations.

What would happen if predators completely exterminated their prey?

Predator populations would eventually collapse due to lack of food.

What is biological control?

The use of natural predators, parasites or pathogens to control pest populations.

Why is biological control preferred to chemical pesticides?

Environmentally friendly, Reduces pollution, Minimises harm to non-target organisms, Maintains ecological balance.

Give an example of biological control.

Ladybird beetles controlling aphids.

Give another example of biological control.

Gambusia fish feeding on mosquito larvae.

What is herbivory?

A special form of predation where animals feed on living plant material.

Why are herbivores considered predators ecologically?

They consume living organisms (plants).

Give examples of herbivores acting as predators.

Cow eating grass, Caterpillar feeding on leaves, Locust feeding on crops.

Why do plants require defence mechanisms?

They cannot move away from herbivores.

What are structural plant defences?

Physical features that discourage feeding.

Give examples of structural plant defences.

Thorns, Spines, Tough leaves.

What are chemical plant defences?

Toxic chemicals produced by plants that deter herbivores.

Give examples of plant chemical defences.

Nicotine, Caffeine, Quinine, Strychnine, Opium, Cardiac glycosides.

How do plant toxins affect herbivores?

Cause illness, Reduce digestion efficiency, Reduce reproduction, May cause death.

How can species coexist despite using similar resources?

Through resource partitioning.

Name three ways resource partitioning occurs.

Resources used at different times, Resources used in different areas, Different parts of the same resource are used.

How does resource partitioning reduce competition?

It reduces direct overlap in resource use between species.

State five key roles of predation in ecosystems.

Transfers energy through food chains, Controls prey populations, Maintains ecological balance, Promotes biodiversity, Drives evolutionary adaptations in predators and prey.

Which predation-related diagrams should you be able to interpret and label?

Predator-prey population graph showing cyclical fluctuations, Ecological pyramid showing energy flow through trophic levels, Camouflage example (e.g. stick insect), Warning colouration example (e.g. Monarch butterfly), Food chains and food webs showing predator-prey relationships.

What are common IEB examination questions on predation?

Interpret predator-prey graphs, Explain density-dependent factors, Distinguish between predator and prey adaptations, Explain biological control, Compare intraspecific and interspecific competition, Explain resource partitioning, Describe the ecological importance of predation, Explain energy flow through food chains and trophic levels.

Give a complete definition of predation suitable for an IEB exam.

Predation is an interspecific interaction in which one organism, called the predator, captures, kills and consumes another organism, called the prey. Predation transfers energy through trophic levels, regulates prey populations, maintains biodiversity and ecological balance, and acts as a density-dependent factor in ecosystems.