Chapter 13 Ecology Parasitism

Parasites

organisms that live in or on other organisms and have a negative effect, they usually have a higher reproductive rate than their hosts, and typically harm but do not immediately kill their hosts

What does a parasite consume?

tissues or body fluids or the organism it lives on (its host)

Macroparasites

Relatively large parasite species, such as arthropods, worms, and pentastomes.

Microparasites

Parasite species too small to be seen with the naked eye, such as bacteria, protists, and fungi.

What can parasites feed on?

Both plants and animals

Ectoparasite

A parasite that feeds on the external surface of a host.

Endoparasite

parasite living on the inside of its host

Fungi ectoparasites

mildews,rusts, and smuts grown on surface and use hyphae to extract nutrients from plant tissues

Most disease causing organisms are

endoparasites

Pros and cons of endo vs ecto parasites

ectoparasites can disperse more easily but are exposed to predators, other parasites, and parasitoids. endo parasites are protected from external environment and can easily access food but can be attacked by hosts immune system

What are some ways hosts defend themselves from parasites?

exoskeletons, skin, immune systems, memory cells that recognize parasites, plants have antimicrobial and antifungal compounds as immune responses

transferrin

a protein that removes iron from blood and stores it so endoparasites cannot get it

Defensive symbionts

fungal symbionts in some plant leaves protect them from pathogen attacks

What selective pressure are parasites under?

strong selective pressure to develop counter defenses

Plasmodium

endoparasite that causes malaria by infecting mosquitos

Challenges plasmodium faces in human hosts

red blood cells do not import nutrients, after infection plasmodium causes red blood cells to have abnormal shape but these cells are destroyed by the spleen

How does plasmodium counterdefend?

hundreds of genes whose function is to modify red blood cells, can add transport nutrients to red blood cells, other genes direct production of knobs that prevent them from reaching the spleen where they would be destroyed

coevultion

population of two interacting species evolve together each in response to selective pressure imposed by the other

Biological control

importation of a pests natural enemies to a new locale where they do not occur naturally relies on animal mechanisms

gene-for-gene interactions

gene response where they are best adapted to cope with the genotype of their locan host/parasite

Trade-offs are

trait that improves host defenses or parasite counter defenses may reduce some other aspect of growth survival or reproduction

How can parasites impact extinction?

can sometimes drive local host populations extinct and reduce their geographic ranges

How can parasites impact host population cycles?

parasite known to decrease survival and reproductive success can cause population crashes

Dynamics and spread of diseases

for disease to spread density of susceptivle hosts must exceed a critical threshold (m/B) need to know number of susceptible individuals (S) infected individuals (I ) and recovered and immune individuals (R), factors and genotype also important

disease transmission equation

B is transmission coefficient and shows how effectively the disease spreads, encounter rate (SI x B). I increases when the disease is transmitted successfully and deceases when individuals die or recover (m rate of death and recovery)

How are susceptibility levels changed in humans?

Vaccinations

How does climate change affect the distribution of diseases?

increasing water temperatures correlated with coral reef, marine, and amphibian disease, mosquitos and other disease vectors are more active in warm conditions

Vector Ecology

vector presence, climate effects on vector populations, host-vector interactions (example: mosquitos)

dominant competitor

species that monopolize use of space

How do parasites alter the outcomes of species interactions?

suppression of dominant species

ecosystem engineers

an organism that modifies creates or destroys habitat and modulates the availability of resources to other species

What is an example of an ecosystem engineer?

Corophium ( shrimp) burrows hold the mud together and prevent erosion that form mud islands at low tide when parasite drives populations to extinction erosion increases and the islands disappear