Diversity and Evolution

Question 1

Define a eukaryote.

Answer 1

Organisms with cells containing membrane bound organelles and have a distinct nucleus in which the genetic information is contained.

Question 2

Describe the levels of taxonomic classification. (Hint: start with ‘Kingdom’).

Answer 2

Kingdom, phylum, class, order, family, genus, species

King Prawn Curry Or Fat Greasy Sausages

Question 3

What are the three main domains of life? Describe the types of linkages in the plasma membranes of all three.

Answer 3

Bacteria- Ester links
Archaebacteria- Ether links
Eukarya- Ester links

Question 4

Briefly describe Darwin’s theory of evolution.

Answer 4

• Random heritable variations in a species
• If there is a selective force, the frequency of alleles may change to favour those with characteristics that make them better adapted to their environment (natural selection).

Question 5

What were the three perceived ‘weaknesses’ at the time of Darwin’s theory of evolution?

Answer 5

• No knowledge of heredity and genetics (didn’t know about Mendel’s work)
• Was their enough time for evolutionary change between forms
• Uncertainty about the age of the earth

Question 6

Describe the two rate of evolution theories: gradualism and punctualism.

Answer 6

Gradualism- gradual diversification over time

Punctualism- diversification in leaps at the ends of long periods of stasis (explains gaps in the fossil record)

Question 7

Give some examples of experimental evidence for evolution.

Answer 7

• Peppered moths, natural selection due to the selection pressure created by their changed environment
• Rapid effects of artificial selection e.g. species gaining pesticide resistance
• Crossing species to give intermediate characteristics

Question 8

What is a cline with the example of flowers?

Answer 8

Where a series of bio-communities show a continuous gradient, e.g. flowering times change with latitude.

Question 9

What is a ring species?

Answer 9

Series of neighboring populations that can interbreed with relatively closely related populations, but for which there exist at least two “end” populations in the series that are too distantly related to interbreed.

Question 10

What are the 4 main geological eras and when did they occur?

Answer 10

Cenozoic era, >65 MYA

Mesozoic era, >250 MYA

Palaeozoic era, > 590 MYA

Precambrian era, >4600 MYA

Question 11

What are the natures of prokaryotic and eukaryotic ribosomes (in terms of S per subunit)?

Answer 11

Prokaryotic- 70S (30S and 50S subunits)

Eukaryotic-80S (40S and 60S subunits)

Question 12

What is peptidoglycan?

Answer 12

Forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall. Made of sugar and amino acids.

Question 13

What is a protist?

Answer 13

Any eukaryotic organism that is not an animal, plant or fungus

Question 14

What is a paraphyletic group?

Answer 14

A paraphyletic group is a group of organisms that includes an ancestor but not all of its descendants.

Question 15

Name ways in which prokaryotic organisms changed to eukaryotic organisms.

Answer 15

• Cell wall lost
• Nuclear envelope forms
• Digestive vacuoles form
• Peptidoglycan lost
• Invagination of cell membranes

Question 16

What is secondary endosymbiosis?

Answer 16

Secondary endosymbiosis occurs when the product of primary endosymbiosis is itself engulfed and retained by another free living eukaryote.

Question 17

What are pseudopods?

Answer 17

Temporary cytoplasm filled projections of eukaryotic cell membranes or unicellular protists. They may be used for motility, or ingesting nutrients or other particulate matter.

Question 18

What are the five clades of eukarya? Give an example of each.

Answer 18

UPRCE (Usar Por Recordar Clades Eukaryotes)

Plantae: -Includes land plants

Unikonts: -Frogs, humans, fungi

Chromalveolates: -Paramecium

Excavates: -Trichomonas vaginalis

Rhizaria:-Amoebas

Question 19

What is a parasitoid? Give an example.

Answer 19

Organism that spends a significant portion of its life on or in a single host (ultimately sterilising or killing the host) e.g. parasitic wasp laying its eggs inside a caterpillar

Question 20

What is a platyhelminth?

Answer 20

An ectoparasite that is a flatworm. Eg salmon fluke. Attach and graze on blood, skin and mucus of fish

Question 21

What are trematoda? Describe a disease they cause.

Answer 21

Another class of platyhelminth, an endoparasite. Eg liver fluke.

Snail fever (sheep liver fluke)

• Snail is intermediate host.
• Snail passes on eggs which secrete proteolytic enzymes and enable shedding into faeces
• Sheep eventually die from kidney failure
• Cercariae penetrate tissue and use he circulatory system to spread around the body

Question 22

What are cercariae?

Answer 22

Free swimming larval stage in which parasitic fluke passes from intermediate host to another intermediate host or a final vertebrate host.

Question 23

What are the three important body parts of a tape worm?

Answer 23

• Scolex- specialised front end which contains hooks which hook onto the intestinal wall
• Microtrichs-(like microvilli) to increase surface area for absorption
• Proglottid- Each segment in the tapeworm contains a compete sexual mature reproductive system

Question 24

What is adaptive change in terms of evolutionary mechanisms and allele frequencies?

Answer 24

Where some individuals in a population contribute more offspring to the next generation than others which causes in different allele frequencies. It is adaptive because ti causes the fitness to increase- the parents of the offspring were fitter so produced more offspring.

Question 25

What are the three selection forces and what do they mean?

Answer 25

Directional- Favours characteristics far from the mean

Stabilising-Favours characteristics close to the mean (maintains average phenotype)

Disruptive-changes characteristics of populations by favouring characteristics in both directions away from the mean.

Question 26

What is panmixis?

Answer 26

Random mate choice in sexual reproduction

Question 27

What is inbreeding and outbreeding?

Answer 27

Inbreeding- tendency for self fertilisation or cross fertilisation between closely related individuals- if few in a population then this is better than not breeding at all because its better to pass on those inbred genes than none at all

Outbreeding-Mating between unrelated or distantly related individuals of a species

Question 28

What are the three types of speciation?

Answer 28

Allopatric speciation- distinct geographical or spatial isolation between populations. Reproductive isolation follows the geographical separation.

Sympatric speciation- new species arise within an existing population as a result of behavioural differences associated with specialisations within the population. Reproductive isolation precedes differentiation

Parapatric speciation -It occurs when populations are separated not by a geographical barrier, such as a body of water, but by an extreme change in habitat. While populations in these areas may interbreed, they often develop distinct characteristics and lifestyles.