Parasitism

Question 1

What does the term degenerate mean ?

Answer 1

This is when parasites lack the structures and organs found in other organisms

Question 2

The niche for an ectopsrasite is in the ______ of the host.Give some examples of ectoparasites…

Answer 2

Surface

Lice and ticks

Question 3

What stage is the parasite in when host at when its in the definitive stage ….

Answer 3

This is the host where the parasite reaches sexual maturity

Question 4

In an intermediate host ,the parasite is doing what ?

Answer 4

Completing its life cycle …either carrying out asexual reproduction to greatly increase its numbers or as a means of transmission,making the intermediate host a vector

Question 5

What is a fundamental niche ….

Answer 5

One that the organisms occupies when there are no other species present competing for space or resources… This organisms will occupy the niche in abscene of interspecific competition

Question 6

Explain what the competitive exclusion principle ?

Answer 6

This is when two species are in intense competition with one another ,the niches of the two species are so similar that the weaker of the two species will decline into extinction

Question 7

Mammals have innate or natural ,__________ defence to parasites …

Answer 7

Non specific

Question 8

Give five examples of physical barriers to parasites…..

Answer 8

Skin
Chemical secretions such as mucus and tears
Inflammatory response
Phagocytes
Natural killer cells ( lymphocytes- the white blood cells )

Question 9

When the skin is damaged by a cut or wound,the external barrier becomes warmer and redder - state what this is a result of ….
And - how this helps a suitable defence

Answer 9

This is a result of small blood vessels dilating.This helps defence as it increases blood flow to the wound,thus increasing the amount of white blood cells such as phagocytes.

Question 10

Describe the process of phagocytosis ….

Answer 10

This is a type of non specific defence where the White blood cells phagocytes engulf foreign antigens into vacuoles and digest them using digestive enzymes present in lysosomes

Question 11

What type of cells carry out specific defence ?

Answer 11

White blood cells.These cells also carry out Immune surveillance which is when white blood cells patrol the body ,recognising and destroying foreign antigens.

Question 12

What is an endoparasite ….

Answer 12

This is when the parasite lives within the host such as tapeworms.

Question 13

What are vectors responsible for ?

Answer 13

Transmitting a parasite from one host to another yet may also be a host for the parasite.A good example of a vector is a mosquito transporting the malaria parasite.

Question 14

State the type of niche described below …

The niche that an organism occupies when there is competition from other species.

Answer 14

Realised Niche

Question 15

Parasites have a ________ niche

Answer 15

Narrow

Question 16

A realised niche exists in the presence of ….

Answer 16

Interspecific competition

Question 17

What is the definition of resource partitioning ?

Answer 17

When two different species compromise over resources to reduce competition.The two species manage to do exist.

Question 18

Transmission is the …

Answer 18

Spread of a parasite to a host

Question 19

What term is given to the deleterious effect that the parasite has on the host …

Answer 19

Virulence

Question 20

What are the two conditions that result in greater transmission rates ??

Answer 20

Overcrowding of hosts such as in a busy place …

Means of transmission such as presence of vectors

Question 21

What is the definition of the term extended phenotype ?

Answer 21

A theory whereby the parasites modifies the hosts behaviour to increase its own transmission.

Question 22

How do phagocytes have a role in specific defence ?

Answer 22

As the foreign antigens previously engulfed by phagocytes are pushed back out onto the surface of the phagocyte to present these antigens to lymphocytes.

Question 23

Is a lymphocytes a white blood cell ?

Answer 23

Yes

Question 24

What is the role of B lymphocytes ?

What is the role of T lymphocytes ?

Answer 24

B : produce specific antibodies in response to the specific antigens

T; destroy specific infected or damaged cells by bringing about apoptosis

Question 25

What is clonal selection ?

Explain the process …

Answer 25

The process where by lymphocytes become amplified during mitosis.
Each lymphocyte divides and differentiates into clones- one clone becomes a plasma cell and the other adopts the role of a memory cell.B lymphocyte memory cells are capable of mounting a very quick response by producing the specific antibody required to combat the antigen.This occurs when the individual is exposed to the same parasite a second time.

Question 26

How do endoparasites remain undetected by the hosts immune system ?

Answer 26

As they mimic host antigens and are capable of modifying the host - immune response,preventing the host from mounting and attack .

Question 27

What is antigenic variation and how does this help the parasite stay a step ahead of the immune response ?

Answer 27

When parasites show great amount of variation amongst strains which promotes rapid evolution

Question 28

Epidemiology is the study of …..

Answer 28

The outbreak and spread of infectious disease

Question 29

Give the definition of herd immunity ….

Answer 29

Protection offered to non-immune members of s population by sufficient numbers immune individuals.

Question 30

The density of resistant hosts in the population required to prevent an epidemic is known as what ?

Answer 30

Herd immunity threshold