Book 6: Topic 4

Question 1

What is biological diversity?

Answer 1

Reflected in:
The vast number of species of organisms.
The variation of individual characteristics within a single species.
The variation of cell types with a single multicellular organism.

Question 2

What is the cause for differences between species?

Answer 2

Genetic differences.

Question 3

What is the cause for differences between individuals within a species?

Answer 3

The result of genetic factors, environmental factors or a combination of both.

Question 4

What is a locus?

Answer 4

The particular site on a DNA molecule where a gene is located.

Question 5

What does the genetic code, carried by the base sequence of each gene, determine?

Answer 5

The sequence of amino acids during protein synthesis.

Question 6

The genetic code is the same in all organisms, what does this provide evidence for?

Answer 6

Evolution.

Question 7

What can cause genetic diversity within a species?

Answer 7

Gene mutation, chromosome mutation or random factors associated with meiosis and fertilisation.

Question 8

What results in species becoming better adapted to their environment?

Answer 8

Genetic diversity acted upon by natural selection.

Question 9

What can be used to measure variation within a species?

Answer 9

Differences in the base sequence of DNA or the amino acid sequence of proteins.

Question 10

What can be used to measure biodiversity within a community?

Answer 10

Species richness and an index of diversity.

Question 11

What are prokaryotes?

Answer 11

Unicellular organisms that do not develop or differentiate into multicellular forms.

Question 12

In what way do some bacteria grow?

Answer 12

In filaments or masses of cells. (Each cell in the colony is identical and capable of independent existence).

Question 13

Why might prokaryotic cells be adjacent to one another?

Answer 13

They did not separate after cell division or they remained enclosed in a common sheath/slime, secreted by the cells. (Typically, there is no continuity or communication between the cells).

Question 14

Where are prokaryotes capable of inhabiting?

Answer 14

Almost every place on earth.

Question 15

How are prokaryotes distinguished from eukaryotes?

Answer 15

On the basis of nuclear organisation, specifically their lack of a nuclear membrane.

Question 16

Other than a nuclear membrane, what else do prokaryotes lack that distinguish them from eukaryotes?

Answer 16

Any intracellular organelles and structures.

Question 17

What takes over most of the functions of organelles in prokaryotes?

Answer 17

The prokaryotic plasma membrane.

Question 18

Since there are no organelles in prokaryotic cells, what is the function of the cytoplasm?

Answer 18

Contains all the enzymes needed by the cell for all metabolic reactions.

Question 19

What type of ribosomes do prokaryotic cells have?

Answer 19

The smaller 70 S type.

Question 20

What is the nucleoid/nuclear zone in prokaryotic cells?

Answer 20

The region of the prokaryotic cytoplasm that contains DNA. It is not surrounded by a nuclear membrane.

Question 21

Describe the DNA in the nucleoid of prokaryotic cells.

Answer 21

Always circular, compacted by a mechanism called “supercoiling” and it is not associated with any proteins to form chromatin. (Not to be confused with plasmids).

Question 22

Describe the plasmid in prokaryotic cells.

Answer 22

Small circles of DNA, used to exchange DNA between bacterial cells. (Useful for genetic engineering and have a role in antibiotic engineering).

Question 23

Describe the cell membrane in prokaryotic cells.

Answer 23

Made of phospholipids and proteins, like eukaryotic membranes.

Question 24

Describe the mesosome in prokaryotic cells.

Answer 24

A tightly-folded region of the cell membrane containing all the membrane-bound proteins required for respiration and photosynthesis. (Can also be associated with the nucleoid).

Question 25

Describe the cell wall in prokaryotic cells.

Answer 25

Made of murein (not cellulose as in plant cells), which is a glycoprotein/peptidoglycan (protein/carbohydrate complex). There are two kinds of cell wall that can be distinguished by a Gram stain. Gram positive bacteria - thick cell wall and stain purple. Gram negative bacteria - thin cell wall with an outer lipid layer and stain pink.

Question 26

Describe the capsule/slime layer in prokaryotic cells.

Answer 26

A thick polysaccharide layer outside the cell wall (like the glycocalyx of eukaryotes). Used for sticking cells together, as a food reserve and as protection against desiccation (the removal of water), chemicals and phagocytosis (cell eating).

Question 27

Describe the flagellum in prokaryotic cells.

Answer 27

A rigid, rotating helical-shaped tail used for propulsion. The motor is embedded in the cell membrane and is driven by an H+ gradient across the membrane. Clockwise rotation drives the cell forward.

Question 28

What is endosymbiosis?

Answer 28

The idea that the organelles of the eukaryotic cell could be originally derived from prokaryotic cells that have become incorporated inside other, larger prokaryotic cells.

Question 29

What are the observations that support the idea of endosymbiosis?

Answer 29

Prokaryotic cells are older and more diverse than eukaryotic cells.
Organelles, contain circular DNA and 70 S ribosomes like prokaryotic cells.
Organelles have double membranes, as though a single-membrane cell had been engulfed and surrounded by a larger cell.
Organelles reproduce like prokaryotic cells, by binary fission.
Organelles are very like some bacteria that are alive today.

Question 30

How much larger are eukaryotic cells compared to prokaryotic cells?

Answer 30

About 10x the size and as much as 1000x greater in volume.

Question 31

What is the major and extremely significant difference between prokaryotes and eukaryotes?

Answer 31

Eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place.

Question 32

Describe the nucleus in eukaryotic cells.

Answer 32

A membrane delineated compartment that houses the cell’s DNA.

Question 33

What are eukaryotic organism’s specialised structures within the cell?

Answer 33

Organelles, which perform dedicated functions.

Question 34

How many different types of organelles are commonly found in eukaryotic cells?

Answer 34

A dozen.

Question 35

What are some key differences of prokaryotic cell’s DNA from eukaryotic cells?

Answer 35

In the nucleus, DNA molecules are very long, linear and associated with proteins - “histones”.

Question 36

What does a DNA molecule and its associated proteins form, in a eukaryotic cell?

Answer 36

A chromosome.

Question 37

What is an example of part of the nuclear DNA, in eukaryotes, that does not code for polypeptides?

Answer 37

Non-coding multiple repeats of base sequences between genes.

Question 38

Within a gene, which sequences code for amino acid sequences and which sequences are non-coding sequences?

Answer 38

Exons code for amino acid sequences. Exons are separated by one or more non-coding sequence, called introns.

Question 39

Describe the mitochondria in eukaryotic cells.

Answer 39

A tubular organelle about 8 nano metres long. Surrounded by a double membrane. The outer membrane is simple and quite permeable, while the inner membrane is highly folded into cristae, which give it a very large surface area.

Question 40

What is the function of mitochondria in eukaryotic cells?

Answer 40

It is the location where most of the reactions of aerobic respiration take place.

Question 41

What similarities do mitochondria and chloroplasts in eukaryotic cells share with prokaryotic cells?

Answer 41

Contains short, circular DNA which is not associated with protein.

Question 42

How many mitochondria organelles does a typical eukaryotic cell contain?

Answer 42

1000, though some will contain more depending on their rate of respiration and need for energy.