Predation Flashcards
Resources
Autotrophic organisms
Plants, algae, some bacteria
Photosynthesis or chemosynthesis
Radiation
CO2
Water
Mineral nutrients
Resources
Heterotrophic organisms
6 points
- Animals, fungi, bacteria
- Predators, parasites:
Consume living organisms - Decomposers
Consume dead organisms or waste products - Microorganisms are usually the first detritivores to colonise plant detritus Animal detritivores follow later
- Organic material (plant, animal, bacteria)
- Food for heterotrophs is very variable:
Plant material has a high carbon content: C:N ratio 40:1
Bacteria, fungi and animals have a lower carbon content: C:N ratio 10:1
Autrotrophs and inorganic resources
- Plants and other autotrophs assimilate inorganic resources into organic molecules
- These become the resources for heterotrophs
Animals as food
- Herbivores and carnivores have very similar body composition
- Animal tissues:
contain no structural carbohydrate or fibre
are rich in lipid and protein
- The main excretory products of carnivores are nitrogenous
Plants as food
5 points
- Herbivores and detritivores that consume plant material have food rich in carbon
poor in protein - The waste products are carbon-rich compounds
carbon dioxide
fibre - Most herbivores are limited by lack of nitrogen
- Only a few plant consumers have cellulases
Many fungi, some bacteria and a few protozoa - Some bacteria and protozoa are found in symbiotic association with herbivores e.g. ruminants
Definition of predation
- Predation is the consumption of one organism
(the prey) by another organism (the predator), in which the prey is alive when the predator first attacks it - A predator uses other live organisms as an energy source, removing the prey individuals from the population
- Excludes scavenging and detritivory
Classification of predation
- Food type (Taxonomic classification)
Carnivore, herbivore, fungivore, bacterivore, omnivore - Trophic level
Primary, secondary, tertiary consumer - Food size
Microphage, Macrophage - Prey capture strategy
Pursuit, stalking, ambush, sessile opportunist
Predation
Functional classification
- True predator
- Grazer
- Parasite
- Parasitoid
True predators
4 points
- Kill prey almost immediately
- Usually eat the whole organism
- Eat several or many prey during lifetime
- Usually applied to carnivores
Grazers
4 points
- Usually do not kill prey
- Consume part of the prey organism
- Often attack large numbers of prey
- More herbivore grazers
Parasites
7 points
- Usually do not kill prey
- Consume part of the prey organism (host)
- Attack one or small number of prey
- Much smaller than prey
- Host is habitat and food
- Endo- or Ecto-
- Carnivores and herbivores
Parasitoids
- Part of life cycle (subadult) is parasitic
- Usually kill prey eventually
- Consume all of the host organism
- Attack one prey
- Smaller than prey
- Host is habitat and food
- Endo- or Ecto-
- Carnivores
Effects on the prey individual
True predators –
Parasitoids –
Grazers and Parasites -
True predators – prey killed
Parasitoids – prey killed
Grazers and Parasites
– herbivory example
Effects of herbivory Depends on
2 points
1. Depends on location of attack Leaves Sap Meristem Flower Fruit Root
- Depends on timing of attack
Germination
Setting seed
Effects of herbivory
4 examples of Plant compensation
- Removal of leaves may decrease self shading
- Removal of shaded leaves may improve photosynthesis / respiration balance
- Herbivory on shoot
more photosynthate to shoot - Herbivory on root
more photosynthate to root
Effects of herbivory
what is plant compensation
3 points
- Compensation counteracts harmful effects
- Perfect compensation is rare
- Plants are usually harmed by herbivores
Effects of herbivory
Defensive responses of plants
2 points
- Following herbivore attack plants increase their production of defensive chemicals or structures
2. Larch, defoliated by larch budmoth Zeiraphera diniana, have: delayed leaf production tougher leaves higher fibre and resin content lower nitrogen content
Effects of herbivory
Disproportionate effects
2 points
- Ring-barking
Goats, squirrels, rabbits, voles, sheep, slugs - Vectors of plant pathogens
Bark beetles and Dutch elm disease
Aphids and Barley Yellow Dwarf Virus
Effects of herbivory
Effects on the prey individual
3 points
- Herbivores increase mortality
- Herbivores reduce growth
- Herbivores reduce reproduction (fecundity)
Effects on the prey population
Individuals are not attacked at random:
2 points
- Individuals that are preyed upon are those that are least likely to:
Survive
Reproduce - e.g. Populations of Thompson’s gazelles predated by cheetahs and wild dogs
Victims
Mostly younger age classes
Make no contribution to reproduction yet
Effects on the prey population
Prey refuges
- If a predator does not drive prey to extinction there must be a prey refuge.
- This could include:
Intra / interspecific competition between predators
Predator behaviour (e.g. aggregation in patches)
Inaccessible (micro) habitat
Hiding place
Escape response
Defence response
Effects on the prey population
Populations may compensate for losses - woodpigeons
- Predation reduces intraspecific competition
- Shooting woodpigeons does not increase overall winter mortality
- Populations are limited by food
- Shooting reduces competition & natural mortality
- Density dependent immigration occurs
- Population size determined by density dependent intraspecific competition for food
Effects on the prey population
Populations may compensate for losses - grasses
2 points
- Grasses, such as cereals can sustain considerable losses of individuals and compensate by tillering
- Crops ‘sown to a stand’ e.g. sugar beet cannot sustain loss of individuals without reduction of yield
Effects on predators
Consumption rate
2 points
- Increase in food available / consumed leads to an increase in:
Survival
Growth
Reproduction - Reduces the effects of competition
- Consumption must exceed lower threshold
- Consumers become satiated (plateau)
Effects on predators
Diet width Specialists
5 points
- may attack parts of prey
- may attack several species or one species
- Avoid interspecific competition
- At risk if food becomes scarce
- Parasites and parasitoids are often highly specialised
Effects on predators
Diet width generalists
4 points
- feed on range of food
- May be exposed to interspecific competition
- Can vary diet to suit food availability
- True predators and grazers
usually have relatively broad diets
consumer’s functional response
The relationship between an individual’s consumption rate and food availability
Functional response type 1
- Consumption rate rises linearly with prey density
- Capture rate determined by prey density
- At high prey densities consumption rate remains constant
- Handling time is limiting
Functional response type 2
5 points
- Consumption rate rises with prey density
- Finding prey becomes easier
- At high prey densities consumption rate remains constant
- Handling time is limiting
- Most frequently observed type
Functional response type 1
2 points
- At low densities Type 3 response has an acceleration phase – curve is sigmoidal
Caused by changing efficiency e.g. switching
- At high prey densities Type 3 is like Type 2
Causes are the same
Distribution of predators and prey
3 points
- For consumers the world is heterogeneous
- Consumers select patches containing their food
- Consumers select patches with most or highest
quality food
[ predator mite and herbivorous mite. predator introduced both die. solution make habitat more patchy to stop predator eating all herbivores]
