P2 Classification and Evolution

Question 1

What is the biological classification system?

Answer 1

• Grouping living organisms based on similar anatomical features.
• These are hierarchal (grouped from most general, to most specific).

Question 2

How many taxonomic groups does the biological classification system contain, and name these taxonomic levels.

Answer 2

7:
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 3

What is the binomial name of a species, and what advantages does this have?

Answer 3

• Genus species
• Binomial names are universally accepted.
• They also specify which genus the organism belongs to.

Question 4

What is the modern classification system?

Answer 4

• Grouping living organisms based on DNA, RNA and proteins of different organisms.

Question 5

How many kingdoms were organisms originally classified into, and what were they?

Answer 5

5 kingdoms - based on observable characteristics from a light (then later electron) microscope:
- prokaryota
- protoctista
- fungi
- plantae
- animalia

Under the 5 kingdom system, prokaryota are all prokaryotes, and the other 4 kingdoms are all eukaryotes (all contain a nucleus).

Question 6

Characteristics of prokaryota (original kingdoms)

Answer 6

• Unicellular
• No membrane-bound organelles or nucleus
• Contain a cell wall
• Heterotrophic and autotrophic
• 70S ribosomes

Question 7

Characteristics of protoctista (original kingdoms)

Answer 7

• Mostly unicellular, few multicellular.
• Contain membrane-bound organelles and a nucleus
• Mostly no cell walls
• Heterotrophic and autotrophic
• 80S ribosomes

Question 8

Characteristics of fungi (original kingdoms)

Answer 8

• Uniceullular or multicellular
• Contain membrane-bound organelles and a nucleus
• Cell wall (made of chitin)
• Heterotrophic
• 80S ribosomes

Question 9

Characteristics of plantae (original kingdoms)

Answer 9

• Multicellular
• Contain membrane-bound organelles and a nucleus
• Cell wall (made of cellulose)
• Autotrophic
• 80S ribosomes

Question 10

Characteristics of animalia (original kingdoms)

Answer 10

• Multicellular
• Contain membrane-bound organelles and a nucleus
• No cell wall
• Heterotrophic
• 80S ribosomes

Question 11

What changes have been made to the 5 kingdom system recently?

Answer 11

• Scientists divided prokaryota into two kingdoms: eubacteria and archea-bacteria, creating 6 kingdoms.
• They have all of the same characteristics, except eubacteria has a cell wall made of peptidoglycan, and archeo-bacteria has a cell wall that is not made of peptidoglycan.
• Scientists concluded that all eukaryotes (the 4 remaining kingdoms) were very similar, whereas eubacteria and archeo-bacteria were very different from those kingdoms, and from each other. Therefore an extra layer of classification as added above kingdoms (domains).

Question 12

What is the domain system?

Answer 12

• Organisms are in one of 3 domains: archea, bacteria or eukarya.
• This resulted in the 6 kingdom, 3 domain system that is used today.

Question 13

What are the causes of variation?

Answer 13

1. Genetic factors eg. different alleles or mutations can lead to genetic variation.
2. Environmental factors eg. different soil pH or temperatures can lead to environmental variation.

Question 14

What is variation, and what are the types of variation?

Answer 14

• Variation is differences in characteristics between organisms.
• Interspecific variation is differences between organisms of different species.
• Intraspecific variation is differences between organisms of the same species (same species meaning they produce fertile offspring, have a similar appearance and similar genetic makeup).

Question 15

What are the two types of intraspecific variation?

Answer 15

1. Discontinuous variation - results in distinct characteristics eg. blood groups, meaning they are controlled by one or two genes that are not affected by environmental factors.
2. Continuous variation - results in a range of characteristics eg. height, controlled by many genes (polygenic) that are affected by environmental factors.

Question 16

What is an adaption?

Answer 16

A characteristic that evolved in response to the organisms specific environment that increases an organism’s chances of survival and reproduction.

Question 17

What are the 3 types of adaptions?

Answer 17

1. Anatomical - structural or physical characteristics of an organism eg. a tigers stripes create camouflage, allowing it to blend into it’s environment.
2. Behavioural - ways an organism behaves eg. a peacocks courtship behaviour, increasing it’s chances of finding a mate and reproducing.
3. Physiological adaptations - biological processes within an organism eg. human sperm cells contain many mitochondria to improve their chances of moving towards an egg cell and fertilising it.

Question 18

What is convergent evolution?

Answer 18

• When organisms that don’t share a common ancestor show similar characteristics due to adaptation to similar environments.

Question 19

What is evolution?

Answer 19

• A process by which organisms change over time.
• Evolution occurs by natural selection (organisms that are better adapted to their environment have a higher chance of surviving and reproducing, and passing on alleles to their offspring).
• Different characteristics are due to mutations, these are exposed to selection pressures from the environment (factors affecting an organisms chances of surviving and reproducing).
• If these characteristics are advantageous, the organisms is more likely to survive and reproduce, passing on the alleles that code for these characteristics to their offspring, and their offspring will therefore also have a greater chance of surviving and reproducing, increasing the frequency of advantageous alleles with every generation.

Question 20

What is the evidence of evolution by natural selection?

Answer 20

• Fossils show similarities between extinct and current species.
• Molecular evidence: similarities in DNA, cytochrome c (a protein in the electron transport chain in respiration found in all eukaryotic organisms), order of amino acids.