Class #13 - Interspecific Interactions (pt. 2)

Predation

is the consumption of one living organism by another

heterotroph

is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter

carnivore

consume animal tissue

herbivore

consume plant or algal tissue

omnivore

consume plant and animal tissue

true predator

a predator that kills its prey immediately upon capture more or less

What Herbivores are True Predators?

Seed Predators & Planktivores

Parasite

organisms that feed on the live host organism and are not always lethal

Parasitoids

attack the prey indirectly by laying eggs on the hosts body

Describe the predator-prey cycles and why they occur.

Predators directly affect prey mortality rates through total consumption
• Prey directly affect predator birth/death rates
• Form modeled by L-V predator/prey mode

Indirect effects of predators

Predators may indirectly affect prey birth/mortality rates through effects on prey behavior

apparent competition

a shared predator can make it appear the two species compete when they don’t

competitive release

a predator can reverse competitive exclusion

trophic cascade

A predator of an herbivore can help a plant! (The enemy of my enemy is my friend)

symbiosis

the intimate and protracted association between two or more individuals of different species The result of association may be negative (-), positive (+), or benign (0)

  If parasites are not normally lethal: How do parasites impact the host?              

stunted growth • emaciation • behavior modification • sterility

And what would the host normally die from if related to the parasite?

The host may die from a secondary infection

How to parasites compare to their host?

Parasites generally • are much smaller than the host • are highly specialized • reproduce more quickly and in larger numbers than the host

What types of organisms are considered parasites?

Viruses, bacteria, protist, fungi,plants, invertebrates and even vertebrates

an example of mutualism that is symbiosis

cleaner fish and client fish

an example of mutualisms that is NOT symbiosis

flowering plant and animal pollinators

symbiosis must require organisms to…

live together

describe the plant-mycorrihize mutualism

Mycorrhizal fungi provide plants with greater access to inorganic nutrients (e.g., N and P) in exchange for photosynthetic products • > 90% of terrestrial plants involved • Both organisms benefit from enhanced nutrition • This is an example of symbiosis!

When can mycorrhizae be a parasite?

Mycorrhizae can be considered parasitic when the balance of the symbiotic relationship shifts, meaning the fungus takes more nutrients from the host plant than it provides, often occurring when the soil is already rich in nutrients, causing the plant to provide more carbon to the fungus than it receives benefits from in terms of nutrient uptake; essentially, when the "cost" to the plant outweighs the "benefit" of the mycorrhizal association.