4.3 - Classification and Evolution

Question 1

Define species.

Answer 1

A group of organisms with similar characteristic and alleles and can breed to produce fertile offspring.

Question 2

What are the basics of the taxonomical hierarchy?

Answer 2

Organisms are classified into groups, which are subdivided into more groups.
Organisms are classified in terms of similar or shared features, these may be obvious or determined by biochemical or genetic tests.
There is no overlap between groups, it can either be one or the other and cannot fall halfway between groups.

Question 3

What is the taxonomic hierarchy?

Answer 3

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Question 4

What are the rules for naming a member of a species?

Answer 4

Genus part of the name has an upper case first letter, species part of the name has a lower case first letter.

Question 5

Compare the new 3 domain system with the older 5 kingdom system.

Answer 5

Kingdom – organisms placed into one of the following groups: Animalia, Plantae, Fungi, Protoctista & Prokaryotae.
Domains - Prokaryotes (cells without a nucleus) are now divided into 2 domains – Archea and bacteria. Eukaryotes (cells with a nucleus) are placed in the domain Eukarya.

Question 6

Why was the classification system changed & the 3 domain system introduced?

Answer 6

New evidence, mainly molecular showed large differences between Archea & Bacteria – evidence suggests that these two groups evolved separately. The classification system changed to reflect this new evidence.

Question 7

What is phylogeny and what can it tell us?

Answer 7

The study of the evolutionary history of groups of organisms. All organisms have evolved from shared common ancestors. It tells us who’s related to whom and how closely related they are.

Question 8

In what ways can we compare organisms other than observable (anatomical) features?

Answer 8

Molecular evidence. Compare amino acid sequences in common proteins e.g cyctochrome c or Hb. Compare DNA base sequences between species.
Behavioural evidence – similarities in behaviour & social organisation.

Question 9

Why are organisms adapted to their environment & how do they develop?

Answer 9

To increase their chances of survival and reproduction. Adaptations develop because of evolution by natural selection – best-adapted individuals survive, reproduce & pass on their adaptations to their offspring.

Question 10

Describe behavioural, physiological & anatomical adaptations.

Answer 10

Behavioural - the way an organism acts increases its chance of survival.
Physiological – processes inside an organism’s body increase its chances of survival.
Anatomical – structural features of an organism’s body increase its chances of survival.

Question 11

Why do the marsupial & placental mole look similar but are not closely related?

Answer 11

Due to convergent evolution – they have evolved similar characteristics independently of one another due to adapting to similar environments & ecological niches – in two different continents.

Question 12

What is an ecological niche?

Answer 12

The role of an organism within its habitat, e.g. what it eats, when & where it feeds.

Question 13

Which two scientists contributed in formulating the theory of evolution by natural selection?

Answer 13

Charles Darwin & Alfred Wallace.

Question 14

Why are people more aware of Darwin than Wallace?

Answer 14

Interest in this subject by the public came only after the book ‘On the origin of species’ was published by Darwin.

Question 15

Describe the theory of natural selection.

Answer 15

Individuals within a population show variation in their phenotypes. Selection pressures create a struggle for survival. Individuals with better adaptations (to the selection pressures present at the time) are more likely to survive, reproduce & pass on their advantageous alleles to their offspring. Over time the frequency of the advantageous allele increases in the population.

Question 16

What evidence is there to support natural selection?

Answer 16

Fossil evidence, DNA evidence and molecular evidence.

Question 17

What information can be gained from fossils?

Answer 17

Fossils are the remains of organism preserved in rocks.
They can be arranged in chronological (date) order.
Gradual changes can be observed over time & provide evidence for evolution. E.g. The fossil record for horses shows a gradual change in characteristics, including increasing size and hoof development.

Question 18

What information can be gained from DNA evidence?

Answer 18

Closely related species diverged (evolved to become different species) more recently.
Over time gradual changes occur in the base sequence of an organism’s DNA.
Organisms that diverged away from each other more recently, should have more similar DNA, as less time has passed for changes to take place.

Question 19

What information can be gained from molecular evidence?

Answer 19

In addition to DNA, similarities in other molecules provide evidence e.g. protein amino acid sequence or antibodies.
Organisms that diverged away from each other more recently have more similar molecules.

Question 20

What proteins are commonly used for DNA sequencing and why?

Answer 20

Haemoglobin and cytochrome c. They are present in all eukaryotes.

Question 21

Why are molecular comparisons often better than morphological comparisons?

Answer 21

Organisms with the same niche requirements often have adapted in a similar way morphologically – this is called convergent evolution.
Molecular comparisons avoids confusion posed by morphological adaptations.

Question 22

Explain pesticide resistance in insects.

Answer 22

There is variation in a population of insects.
Genetic mutations may result in alleles that make some insects more resistant to a pesticide.
When humans present this selection pressure (the pesticide) to the insects, those with the advantageous allele survive, reproduce & pass on this advantageous allele to their offspring.
Over time the frequency of this advantageous allele increases in the population and the insects will evolve by natural selection.

Question 23

Why is pesticide resistance of concern for humans?

Answer 23

Crop infestations with resistant insects – decrease in yield + more pesticides need to be used which are harmful to many insects not just the pests – expensive.
New pesticides need to be developed – takes time & money.
If disease-carrying insects become resistant – risk of the spread of disease.

Question 24

Explain antibiotic resistance in bacteria.

Answer 24

In hospitals, the over-use of antibiotics generates a selection pressure.
Random mutations result in antibiotic resistance. In hospital (where antibiotics present a selection pressure to bacteria) these alleles will be an advantage.
Those with the advantageous allele survive, reproduce & pass on their antibiotic resistant allele to offspring.

Question 25

Why is antibiotic resistance a concern for humans?

Answer 25

Very hard to treat people infected with antibiotic resistant bacteria – it takes time to treat and so the patient suffers for longer or may even die.
New antibiotics/ need to be developed – which takes time & money.

Question 26

What is the difference between interspecific variation & intraspecific variation?

Answer 26

Interspecific – between species.

Intraspecific – within species.

Question 27

What can you determine from the mean variation of samples & the standard deviation?

Answer 27

Mean – variation between samples.

SD – variation within a sample.