Lecture week 13 (11-16) - Notes Interspecies exploitation.docx

Exploitative interactions

Interactions between individuals that increase the fitness of one individual while reducing the fitness of the other.

+/- designated relationship

Consumption

The general term for herbivory, parasitism, and predation.

Herbivory

The consumption of plant material by an animal, which can either reduce (+/-) or increase the fitness of the plant (+/+).

Food is generally more available for herbivores than it is for carnivores as there are more plants available than animals as food.

The digestive tracks of herbivores tend to be of greater length than those of carnivores due to the need to digest more complex components of plant material

Carnivory

The killing and consumption of other animals by a predator.

Predators only hunt and eat when they are confident that they are not being pursed by other animals themselves.

Animals represent a higher quality food items than plants. The mechanical and chemical breakdown of animal tissue demands fewer and more simple digestive specializations.

Predator-Prey Interactions

Interactions between predators and prey, where predators consume prey for food.

Search image

A specific focus on the most abundant or rewarding prey type while ignoring other potential prey.

The utilization of this makes a predator more successful at finding specific prey, often allowing them to notice very small parts of their prey when they are hidden our camouflaged.

Parasitism

A relationship where one individual (parasite) lives in or on another organism (host) without typically killing the host but suffers some reduction in fitness.

Parasitoids

Parasites that eventually kill their host.

Comes in the form of insects that lay their eggs in the bodies of other insects, and the parasitoid larvae consume their host as they grow and develop.

Standing defenses

Permanent defenses present within prey regardless of predator presence.

Inducible defenses

Defenses that appear as a result of predator pressure.

Mechanical defenses

Physical structures or mechanisms that deter herbivory, such as tough epidermis or entanglement devices.

1. Tough epidermis: of seed shells; bark on branches and trunks

2. Entanglement devices: thick waxy cuticle and plant hair on leaves and stems entangles and deters small herbivores

3. Piercing devices

   1. cutting edges in “nutgrass”, a wetland species (silica)

   2. spines and needles in many deciduous plants and cacti where plants act as a source of food and water, because available water is a limited resource

Chemical defenses

Secondary metabolites produced by plants to deter herbivory, such as phenolics, terpenes, and alkaloids.

Mechanical/behavioral defenses of prey

Prey's physical or behavioral adaptations to avoid predation, such as

1. retaliation

2. startling behavior

3. deflection of attack

4. larger size

5. death feigning

6. fleeing

7. crypsis

8. clustering

Nausea induction - chemical defenses

Defense mechanism where prey produce substances that induce nausea in predators.

Counter adaptations

Adaptations developed by herbivores and carnivores to overcome plant defenses or prey mobility, respectively.

Praying mantis

A predatory insect known for its elongated body and front legs that are adapted for catching and gripping prey.

Surprise pounce

A sudden and unexpected movement made by the praying mantis to capture its prey.

Grasp

The action of the praying mantis using its front legs to firmly hold onto its prey.

Bite

The act of the praying mantis using its powerful jaws to deliver a quick and effective bite to immobilize or kill its prey.

The Lotka-Volterra Model of Predator-Prey Interactions

This model predicts that as prey increase, they should become more available to predators. Predator number should then be able to increase to the point where they consume prey at a greater rate than prey are being produced. Then bred

counter adaptions for herbivores

selection of certain plant parts

tough tongue, mouth and gut

mastication apparatus and grinding mills

countering chemical defense

form a mutualism

eat sub-toxic amounts of plants

eat plant before induced defenses are activated and then abandon the plant

countering chemical defense in herbivores

cellulase

alkaline pH

counter adaptions for carnivores

social carnivory

pursuit

luring

sit and wait