A3.1 Diversity Of Organisms

Question 1

What is variation between organisms?

Answer 1

1. No two individuals are identical in all their traits
2. Patterns of variation are complex
3. They are the basis for naming and classifying organisms

Question 2

Why is a classification system important?

Answer 2

To group and organise variation between organisms

Question 3

Define the term species

Answer 3

A group of similar organisms capable of breeding and producing offspring

Question 4

What is the original morphological concept?

Answer 4

Individuals of the same species tend to look more similar to each other than to members of other species.

[the classification of organisms into species is based upon this concept]

Question 5

What is an example of the original morphological concept?

Answer 5

Lions and Tigers:

Two species of large cats closely related but separate species, each with recognisable, distinct characteristics.

Question 6

What did Linnaeus develop?

Answer 6

The binomial nomenclature— a naming convention for species.

Question 7

How is the binomial nomenclature used?

Answer 7

Species are named using both their genus and species name:

Genus comes first, first letter is capitalised and identifies the genus

Species name is second, in lowercase and distinguishes the species

Question 8

What do species in the same genome share?

Answer 8

Common characteristics and similar traits

Question 9

What do species in the same genome share?

Answer 9

Common characteristics and similar traits

Question 10

What is sexual dimorphism?

Answer 10

When males and females within the same species have completely different features and appearance

Question 11

What is the biological species concept and why is it used?

Answer 11

An alternative method for defining species with a basis on ability to interbreed and produce fertile offspring rather than morphology.

Species look too similar too each other or/and sexual dimporphism.

Question 12

What is an example of the biological species concept?

Answer 12

In species interbreeding, offspring produced will be infertile:

Horse+Donkey=Infertile mule (hybrid)—Mule cannot produce offspring with other mule

HOWEVER some cases mules are fertile so rule is not strict

Question 13

Why are there competing definitions of what a species is?

Answer 13

Both concepts, binomial (morphological) and biological have limitations ad biological systems are complex so there are competing definitions.

Question 14

What is an example of diversity in chromosome numbers of plant and animal species (eukaryotes)?

Answer 14

Humans have 46 chromosomes in each diploid cell: 22 pairs of autosomes and 2 sex chromosomes

Chimpanzees have 48 chromosomes in each diploid cell: 23 pairs of autosomes and 2 sex chromososmes

[chimpanzees are our closest living relative, we share 98% of our DNA)

Question 15

What is speciation?

Answer 15

The formation of new species from the splitting of one pre-existing species into two or more new species.

Question 16

How does speciation occur?

Answer 16

Gradual long term process after physical splitting of a population.

Question 17

What is a cause of speciation?

Answer 17

1. Reproductive barriers preventing interbreeding between 2 populations
2. Physical barriers preventing interbreeding
3. Change in behaviour or timing around reproductive cycles
4. Occasionally changes in chromosome number resulting in sew species

Question 18

What is karyotyping?

Answer 18

Determining and analysing the karyotype of an individual

Question 19

What is the karyotype of an individual?

Answer 19

Banding patterns, length, and centromere position of a chromosome

Question 20

How is a karyogram done?

Answer 20

Isolating condensed chromosomes taken from actively dividing cells.

Individual chromosomes are stained to highlight banding patterns.

The location of centromere (central region of chromosome pair where two copies of same chromosome stay attached to each other) seen when chromosomes are isolated at the correct point of cell division.

Question 21

Why do our closest living relatives have different chromosome numbers, what are the 3 pieces of evidence?

Answer 21

We know that speciation events, including changes in chromosome number happen slowly over time.

When a human karyogram is compared to a chimpanzee karyogram we see:

1. Genes of chromosome 2 closely match those of the the two suspected fusion chromosomes in chimpanzees
2. Telomeric (repetitive sequences that help protect ends of chromosomes from damage) DNA found at fusion region of chromosome 2
3. There is a second centromere region (site where cell’s cytoskeleton attaches to chromosome during cell division) that has mutated and does not function

Question 22

What is the hypothesis for how humans and chimpanzees speciated?

Answer 22

At some point chromosomes 12 and 13 of the chimpanzee karyotype fused, creating chromosome 2 in the human karyotype.

Question 23

What is the genome?

Answer 23

All of the genetic information of an organism

Question 24

What is the cause of some diversity in the genome of the same species?

Answer 24

Variation such as SNPs

Question 25

What are the 2 ways in which genomes differ between species?

Answer 25

Large differences in genome between species due to size and base sequence.

Size of genome: amount of genetic material

Base sequence of genome: determines how DNA is expressed and organisms phenotype

Question 26

What is genome sequencing?

Answer 26

Process of determining order of the bases in an organisms genetic code

Question 27

Weaknesses of genome sequencing and current advanced?

Answer 27

Costly, slow process that is becoming more accessible and less expensive thanks to advances in technology.

Question 28

What are potential future uses of genome sequencing?

Answer 28

Medicine: ability to create personalised medical treatments and interventions based on sequencing of out genome

Question 29

What are current uses in genome sequencing?

Answer 29

Comparison of genomes for revision of classification system, evolutionary relationships.

Question 30

What is the reason for interbreeding dot producing fertile offspring? (HL)

Answer 30

Mismatch in chromosome number, unlikely to produce offspring in parent chromosome numbers.

[e.g. mule end up with uneven chromosmes=infertile]

Question 31

What is a limitation of applying the biological species concept? (HL)

Answer 31

Not applicable to asexually reproducing species or when offspring are genetically identical to parents.

For example, prokaryotes reproduce asexually through binary fission.
Hydra reproduce asexually through budding and offspring are genetically identical to parents.

Question 32

What is horizontal gene transfer? (HL)

Answer 32

Where genetic material is exchanged between individuals rather than passed on between generations (bacteria)—> has led to huge amounts often of genetic variation between prokaryotes despite asexual reproduction.

Question 33

What is a dichotomous key and when is it used? (HL)

Answer 33

Tool used to identify species in field experiments. Series of questions based on physical characteristics with only 2 possible answers.

Question 34

What is DNA barcoding? (HL)

Answer 34

Method of environmental sampling for biodiversity of habitats to be investigated rapidly:

Unknown specimen collected and DNA extracted.
From sample, sequences of DNA identified, creating a unique barcode.
Barcode compared to catalogue of barcodes for identification of species.