Human Biology - Parasites

Front 1

Define the word Parasite:

Back 1

Parasites (endo-) or (ecto-) feed on living organisms (host) while causing harm.

Front 2

What benefits do they gain from them?

Back 2

unlimited supply of nutrients, H2O, constant temperature.

Front 3

How do the mouthparts adaptations benefit them?

Back 3

Allow attachment to host.
Allow use of host's food supply, blood or tissues.

Front 4

Explain how parasites have specialist reproductive strategies.

Back 4

May have male and female reproductive systems
May reproduce asexually
May produce large amounts of eggs/larvae

Front 5

Why do parasites have a reduction of unnecessary sensory organs and locomotory organs in adult stage?

Back 5

Not required as they live in protected, optimum conditions.

Front 6

How do parasites adapt their antigens?

Back 6

Inaccessible to immune system (gut).
Adapt antigens from host (host recognizes parasite as own tissue).

Front 7

What is Toxocara?

Back 7

Roundworms that live in the small intestine of dogs.

Front 8

Describe the lifecycle of the Toxocara?

Back 8

Eggs hatch into larvae and cross intestinal wall.
Distributed in body tissues but remain dormant (inactive).
Larvae are reactivated in pregnant female dogs.
Cross placenta or mammary glands → infect offspring.

Front 9

What happens to the Toxocara once its infected a puppy?

Back 9

Produce eggs and are excreted in faeces
Some larvae spread to lungs, are coughed up, and swallowed back to small intestine
This way, puppies can infect humans by licking their face

Front 10

Explain what happens when it enters humans:

Back 10

Larvae migrate to body organs but cannot reproduce.
Often they only cause constitutional symptoms.
Severe or repeated infections may cause swelling of organs.
May enter eye and cause reduced vision or blindness.

Front 11

State the adaptation of the Toxocara:

Back 11

Sticky eggs increase infection.
Attaches to intestine by hooks.
Lacks unnecessary organs.(locomotory, nervous system)
Produces large amount of eggs to increase infection.
Anaerobic respiration allows survival in intestine.
Produces enzymes that prevent degradation by host's digestive enzymes.
Larvae form cysts around them which allows them to hide from immune system.