Diversity Of Life

Question 1

First lines of defence?

Answer 1

Skin- antimicrobial sebum 3-5 pH
Blood clots and scabs if broken
Mucus- in respiratory, digestive and reproductive tracts
Trap pathogens, released by goblet cells and swept by cilia. Contains lysozyme and phagocytes
Ear wax
Nose hairs
Lysozyme in tears (breaks down cross links between peptidoglycan molecules)
Expulsive reflexes- vomit, diarrhoea, cough, sneeze
Stomach- acidic, gut flora compete with pathogens

Question 2

What are antigens?

Answer 2

On outer surface of cells
Usually proteins or glycoproteins
Foreign antigens cause an immune response

Question 3

Inflammation and the immune system

Answer 3

1) tissue is damaged
2) mast cells release histamine
3) macrophages release cytokines
4) body temperature rises to reduce the rate of reproducing pathogens

Histamine widens capillaries and increases permeability. This allows plasma and white blood cells to enter the tissue.

Neutrophils digest the pathogen and cell debris.

Question 4

Phagocytes (neutrophils) and the immune system

Answer 4

1) phagocytes recognises antigens on pathogen as foreign
2) pathogen engulfed by endocytosis
3) a vacuole (phagosome)surrounds the pathogen
4) the phagosome fuses with a lysosome
5) pathogen destroyed and debris released by exocytosis

Question 5

Interferons and the immune system

Answer 5

Interferons are glycoprotein signalling molecules released by the body cells that have been infected with a virus.
They diffuse to surrounding cells and inhibit viral replication, limiting the spread.
They promote inflammation
They activate macrophages (type of phagocyte)

Question 6

Macrophages and the immune system

Answer 6

Same as with phagocytes but rather than exocytosis, fragments of bacterial antigens (epitopes) are presented on the cell surface in a complex with MHC II proteins. This signals to the adaptive immune response.

Question 7

What are white blood cells?

Answer 7

Lymphocytes

B cells and T cells

Question 8

What are B cells?

Answer 8

Lymphocytes that become activated to secrete antibodies

Made in bone marrow

Question 9

What are plasma cells?

Answer 9

Type of B cells that produce the majority of antibodies

Question 10

What are antigen presenting cells?

Answer 10

Cells that present captured antigens to T cells

Question 11

What are T cells?

Answer 11

Type of lymphocytes that play a central role in the adaptive immune response

Question 12

What are T helper cells?

Answer 12

Guide cytotoxic T cells to pathogens

Made in the bone marrow but mature in the thymus

Question 13

What are cytotoxic T cells?

Answer 13

Lymphocytes that destroy pathogens

Question 14

What are memory T cells?

Answer 14

Lymphocytes that rapidly differentiate into helper and cytotoxic T cells

Question 15

Differences between humoral and cell-mediated immunity?

Answer 15

B

Question 16

What is the humoral immune response?

Answer 16

1) macrophage engulfs bacteria and presents its antigens on the surface, becomes APC
2) APC binds to T helper cell by complementary receptors
3) T helper cell divides to form T memory cells and active T cells
4) stimulate other B and T cells
Or
1) pathogen binds to B cells with complementary receptor
2) B cell comes APC
3) an activated T helper cell with complementary receptors binds to APC. Producing cytokines that stimulate the B cell

Question 17

Linnaean classification order?

Answer 17

Domain
Kingdom 
Phylum
Class
Order
Family
Genus
Species

Question 18

Binomial nomenclature rules

Answer 18

Genus- italics with a capital
Species- italics with no capital
Underline if handwritten

Sp- one species
Spp- multiple species

Question 19

Why use binomial nomenclature?

Answer 19

Unique
Precise
Reflects evolution

Question 20

Biological species definition?

Answer 20

Organisms that can reproduce to produce fertile offspring

Question 21

Limitations of biological species definition

Answer 21

Asexual reproduction
Extinct organisms
Geographically isolated
Fertile hybrids

Question 22

Convergent evolution

Answer 22

Organisms that aren’t closely related independently evolve similar traits because they are adapted to similar environments (same selection pressures)

Question 23

Limitations of classification by morphology

Answer 23

Convergent evolution

Members of the same species can look different

Question 24

Animalia kingdom

Answer 24

Eukaryotic
Multicellular 
Heterotrophic (can’t make own food)
No chlorophyll 
No cell walls
Motile

Question 25

Plantae kingdom

Answer 25

Eukaryotic
Multicellular 
Autotrophic 
Chlorophyll 
Cells walls made of cellulose

Question 26

Fungi kingdom

Answer 26

Eukaryotic
Multicellular or unicellular 
Cells walls made of chitin 
Saprophytic (release enzymes onto dead matter)
No chlorophyll 
Cytoplasm is multinucleate

Question 27

Eubacteria kingdom

Answer 27

Prokaryotic 
70s ribosomes
Unicellular 
Peptidoglycan cell walls
Autotrophic or heterotrophic

Question 28

Protoctista kingdom

Answer 28

Eukaryotic 
Mostly unicellular
Autotrophic or heterotrophic 
Cell walls present, but not always cellulose 
Such as seaweed, amoeba

Question 29

Molecular phylogeny

Answer 29

Molecular phylogeny (evolutionary relationship) is now the standard approach to identify and classify all organisms
Similarities in biological molecules between organisms
Organisms that diverged recently will have the most similar sequences (less time for mutations to alter the sequence)