B6 inheritance, variation and evolution

Question 1

what process are gametes produced by?

Answer 1

meiosis

Question 2

how many cell divisions does meiosis involve?

Answer 2

2

Question 3

where does meiosis happen in humans?

Answer 3

the reproductive organs

Question 4

what are the 4 stages of meiosis?

Answer 4

1. before the cell starts to divide, it duplicates its genetic information, forming two armed chromosomes - one arm of each chromosome is an exact copy of the other arm. after replication, the chromosomes arrange themselves into pairs
2. in the first division the chromosomes pairs line up in the centre of the cell.
3. the pairs are then pulled apart so each new cell only has one copy of each chromosome. some of the father’s chromosomes and some of the mother’s chromosomes go into each new cell
4. in the second division, the chromosomes line up again in the centre of the cell. the arms of the chromosomes are pulled apart

Question 5

what are the products of meiosis?

Answer 5

four gametes, each with only a single set of chromosomes in it. each of the gametes is genetically different from the others because the chromosomes get shuffled up during meisosis and each gamete only gets half of them, at random

Question 6

what is classification?

Answer 6

organising living organisms into groups

Question 7

traditionally, what system have organisms been classified according to?

Answer 7

the linnaean system

Question 8

when was the Linnaean system first proposed and by whom?

Answer 8

it was first proposed in the 1700s by Carl Linnaeus

Question 9

how does the linnaeas system group living things?

Answer 9

according to their characteristics and the structures that make them up. living things are first divided into kingdoms (e.g. the plant kingdom), and then the kingdoms are subdivided into smaller and smaller groups - phylum, class, order, family, genus, species

Question 10

what were the reasons for scientists putting forward new models of classification?

Answer 10

knowledge of the biochemical processes taking place inside organisms developed and microscopes improved (which allowed us to find out more about the internal structures of organisms

Question 11

who proposed the three-domain system and when?

Answer 11

Carl Woese in 1990

Question 12

what led Carl Woese to propose the three-domain system?

Answer 12

evidence gathered from new chemical analysis techniques such as RNA sequence analysis, he found that in some cases, species thought to be closely related in traditional classification systems are in fact not as closely related as first thought.

Question 13

what are the three domains in the three-domain classification system?

Answer 13

1. Archaea - organisms in this domain are primitive bacteria. They’re often found in extreme places such as hot springs and salt lakes
2. Bacteria - this domain contains true bacteria like E. coli and Staphylococcus. Although they often look similar to Archaea, there are lots of biochemical differences between them
3. eukaryota - this domain includes a broad range of organisms including fungi, plants, animals, and protists

Question 14

what smaller groups are the three domains of the three-domain system subdivided into?

Answer 14

kingdom, phylum, class, order, family, genus, species

Question 15

what system are organisms named according to?

Answer 15

the binomial system

Question 16

how does the binomial system work?

Answer 16

every organism is given its own two-part latin name. the first part refers to the genus that the organism belongs to. this gives you information on the organism’s ancestry. the second part refers to the species. e.g. humans are known as homo sapiens - ‘homo’ is the genus and ‘sapiens’ the species

Question 17

what is the benefit of the binomial system?

Answer 17

it is used worldwide an means that scientists in different countries or who speak different languages all refer to a particular species by the same name - avoiding potential confusion

Question 18

what do evolutionary trees show?

Answer 18

evolutionary relationships - how scientists think different species are related to each other. they show common ancestors and relationships between species. the more recent the common ancestor, the more closely related the two species - and the mre characteristics they’re likely to share

Question 19

what type of data do scientists analyse to work out evolutionary relationships for living organisms?

Answer 19

the current classification data (e.g. dna analysis and structural similarities)

Question 20

what type of data do scientists analyse to work out evolutionary relationships for extinct organisms?

Answer 20

they use information from the fossil record