L17: Food chains

Plants prevent predation using:

• spines

• thorns

• toxins/anti-nutrients

Predation encourages:

• pollination

• seed dispersal

Herbivores prevent predation using:

• speed and agility (escape)

• large groups (distraction)

• camouflage, burrowing, crepuscular/nocturnal (avoidance)

• toxins, false toxin-colouration (deter)

Carnivores prevent (or enable) predation using:

• claws/talons

• beaks/teeth

• horns

• venomous bite/scratch/sting

Venom for Defence or Attack in the slow loris

1. When provoked to activate its venom the slow loris raises its arms

2. The brachial gland contains the venomous fluid

3. Needs saliva to be activated

4. In this defensive position the loris can easily access this gland and apply saliva

5. Spreads venom on the head (defence) or keeps in the mouth to bite

Trophic (feeding) levels:

1. Producers: plants/algae/phytoplankton (photosynthesis)

2. Primary consumers: herbivores (eat plants/algae)

3. Secondary consumers: omnivores/carnivores (eat herbivores)

(a) Tertiary consumers: omnivores/carnivores (eat omnivores/carnivores)

(b) Apex predators: tertiary consumer with no predators

4. Decomposers & Detritivores

Autotrophs

An organism that produces its own food (nutrients) using light, water, carbon dioxide, and another simple chemical compounds

Heterotrophs

An organism that cannot produce its own food and instead consumes plant and animal matter as a source of nutrients

Producers examples

• plants (monocots, dicots, trees, moss, lichen)

• algae

• phytoplankton

• not fungi (decomposer)

Characteristics of producers

Autotrophs

• ‘make’ their own food

• create chemical energy from solar/light energy

• photosynthesis = H2 O + CO 2 –-(light) sugars + O

Characteristics of primary consumers

Heterotrophs

• Must eat food to derive/absorb nutrients

• herbivores eat producers

Characteristics of secondary consumers

Heterotrophs

• Must eat food to derive/absorb nutrients

• omnivores/carnivores that eat herbivores

Characteristics of tertiary consumers

Heterotrophs

• Must eat food to derive/absorb nutrients

• omnivores/carnivores that eat other omnivores/carnivores

Characteristics of apex predators

Heterotrophs

• Must eat food to derive/absorb nutrients

• omnivores/carnivores that eat other omnivores/carnivores

• no (wild) predators (top of the food chain)

• vital to their ecosystems (‘keystone species’)

Characteristics of decomposers and detritivores

Heterotrophs

• Must eat food to derive/absorb nutrients

• break down or consume decomposing plants/animals

• release inorganic nutrients back into the environment

Decomposers

• Bacteria, fungi, protists

• Absorb and metabolize nutrients on a molecular scale (saprotrophic nutrition)

• Cannot ingest discrete lumps of matter

Detritivores

• Invertebrates and some vertebrates e.g. sea stars, fiddler crabs, terrestrial worms, some catfish species, larval sea lamprey, most larval insects

• Consume detritus (decomposing plant and animal material, and feces)