Chapter-3 Ecology 9/30

Parasitism

symbiotic relationship between two organisms where one organism, the parasite, lives on or in another organism, the host, causing it some harm, and is adapted structurally to this way of life

Parasitoidism

symbiotic relationship between two organisms where one organism, the parasite, is closely associate with its host, causing it to eventually die

Ectoparasites

A parasite that lives on the outside of an organism

Endoparasites

a parasite that lives on the inside of the organism

Prions

A virus that causes a folding of proteins in the brain that leads to early death

Hyperparasitism

Feeds on another parasite

social parasitism

take advantage of social animals

brood parasitism

Host raise young

kleptoparasitism

steals food collected by host

sexual parasitism

becomes attached for to increase its fitness, like anglerfish

Adelphoparasitism

Sibling -parasitism, closely related to host

Horizontal transmission

When a parasite moves between individuals other than parents and their offspring

Vector

An organism that a parasite uses to disperse from one host to another

Vertical transmission

When a parasite is transmitted from a parent to its offspring

Mode of entering the host:

Airborne, sexually, water, infected food, etc. Piercing tissue (e.g., leeches) Reliance on a vector (e.g., malaria)

Ability of parasite to jump between species:

A lethal parasite that specializes on one host
may face extinction; solution is to infect
multiple species (e.g., bird flu, HIV)

Reservoir species:

Species that carry a parasite but do not
succumb to disease. They can be a continuous
source of parasites as other hosts become rare.

Response from and counterattacks to host’s immune system:

Avoiding detection by incorporating into chromosomes (e.g., HIV)
Form protective outer layer (e.g., schistosomes)
Change compounds present on outer surface (Sleeping sickness)

The density and connectivity of the host populations

The more dense and more connected the host, the more likely the parasite
will spread throughout the population

Susceptible-infected -resistant (S-I-R) model

the simplest model of infectious
disease transmission that incorporates immunity

What is S

Number of individuals susceptible
to a pathogen

What is I

Number of individuals that become
infected

What is R

Number of individuals that develop
resistance

What is b

rate of transmission (via contact)
between individuals

What is g

rate of recovery and development
of immunity