✨Module 4: Classification and evolution

Question 1

List the ranks of the taxonomic classification system.

Answer 1

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 2

What are the 3 domains?

Answer 2

Eukarya (eukaryotes) - have nuclei and membrane-bound organelles. Divide by mitosis, can reproduce sexually or asexually.

Bacteria (prokaryotes) - no nucleus, divide by binary fission.

Archaea - single celled prokaryotes first discovered in extreme environments. No nucleus, no murein cell walls, similar size to bacteria, both Archaea and Bacteria have 70S ribosomes.

The base sequences of ribosomal RNA in Archaea show more similarity to the rRNA of Eukarya than Bacteria

The primary structure of ribosome proteins in Archaea show more similarity to the ribosome proteins in Eukarya than Bacteria

Question 3

What are the 5 kingdoms?

Answer 3

Animalia, Plantae, Fungi, Protoctista, Prokaryota

Question 4

Explain each of the 5 kingdoms.

Answer 4

Animalia - multicellular, small temporary vacuole, heterotrophic.

Plantae - always multicellular, cell wall, large permanent vacuole, autotrophic.

Fungi - can be unicellular, cell wall, large permanent vacuole, heterotrophic, no chloroplasts

Protoctista - multicellular and unicellular, some have cell walls, some have vacuoles, chloroplasts, auto and heterotrophic. E.g. amoeba.

Prokaryota - mostly unicellular, cell wall, some have vacuoles, auto and heterotrophic.

Question 5

Classification table for wolf?

Answer 5

Domain = Eukarya
Kingdom = Animalia
Phylum = Chordata
Class = Mammalia
Order = Carnivora
Family = Canidae
Genus = Canis
Species = lupus

Question 6

Why is classification important?

Answer 6

Provides info about an organism, based on members of the same group. Allows accurate identification of an organism.

Question 7

Why have classification systems changed overtime?

Answer 7

=> Living organisms classified into two kingdoms based on major differences in characteristics, for example those that moved and ate (animals) and those that didn’t (plants).
=> Use microscope allowed smaller details to be observed, so organisms divided into 5 kingdoms.
=> Advances in science allowed DNA and proteins to be studied, providing evidence for evolutionary relationships.
Three domain system proposed.

Question 8

Define species.

Answer 8

A group of organisms can reproduce to produce fertile offspring.

Question 9

The binomial name for a species is always …

Answer 9

Underlined when handwritten, italics when typed. It consists of the genus and species name.

Question 10

Define phylogeny.

Answer 10

The evolutionary relationships between organisms. Species with a more recent common ancestor are classified together.

Advances in DNA, RNA and protein sequencing have allowed scientists to classify organisms according to their phylogeny more accurately than using visible characteristics.

Molecular analysis allows scientists to build phylogenetic tree diagrams that show the relationships between organisms.

Question 11

Main difference between early classification systems and phylogeny?

Answer 11

Historical classification systems based on physical characteristics, phylogeny based on evolutionary relationships.

Question 12

Advantages of phylogeny rather than classification system?

Answer 12

=> Phylogeny produces a continuous tree but classification is discrete taxonomical groups, so scientists are forced to put organisms into specific groups that they don’t quite fit.
=> Classification system is misleading as it implies different groups within same rank are equal.
=> Phylogeny is not hierarchical (and bases of evolution) therefore different groups on the tree are represented according to their evolutionary position, so can thus be compared.

Question 13

Fossil evidence for the theory of evolution by natural selection (passing on advantageous alleles).

Answer 13

Fossils are preserved remains of organisms or other features left by organisms, such as footprints, faeces.
The most recent layer is found on the top. Evidence:

=> Fossils of simple organisms like bacteria and found in oldest rocks, whilst fossils of complex organisms are found in most recent rocks.
=> Plant fossils appear before animal fossils. This shows animals require plants to survive.
=> Fossils also allow us to show similarities between extinct species (i.e. how related they are) and even between now-extinct, ancestral species and present-day species.

Question 14

Pro’s and con’s of using fossil record as a source of evidence for evolution.

Answer 14

Pros: radioisotopes can be used to date fossils, changes can be tracked over time.

Cons: many organisms decompose quickly before they fossilise, destroyed by volcanoes/earthquakes.

Question 15

Molecular evidence for the theory of evolution by natural selection.

Answer 15

DNA found in the nucleus of cells can be sequenced and used to provide evidence of evolutionary relationships between species and how the genetic code of species has changed as they have evolved

The differences between the nucleotide sequences in the analogous genes of different species can provide a lot of information:

The more similar the sequence the more closely related the species are.

Two groups of organisms with very similar DNA will have separated into separate species more recently than two groups with less similarity in their DNA sequences.

As a result, DNA sequence analysis and comparison can be used to create phylogenetic trees that show the evolutionary relationships between species.

Question 16

Comparative biochemistry providing evidence for evolution.

Answer 16

Study of similarities and differences in proteins and nucleic acid/DNA of an
organism (1); changes in highly conserved molecules can help identify evolutionary links (1); such as
cytochrome C / ribosomal RNA (1); species that are closely related have the most similar DNA and
proteins /distantly related have far fewer similarities.

Question 17

Difference between interspecific and intraspecific variation?

Answer 17

Interspecific - variation between individuals of different species.
Intraspecific - variation between individuals of the same species.

Question 18

Genetic causes of variation?

Answer 18

=> Genes have different alleles which lead to different characteristics.
=> Mutations (change in DNA base sequence) lead to changes in the protein made. These proteins can affect physical and metabolic characteristics.
=> Meiosis due to independent assortment and crossing over.

E.g. eye colour, blood type, lobed or lobeless ears.

Question 19

Environmental causes of variation?

Answer 19

E.g. scar, tattoo, dyed hair. Could also be darker skin in response to sunlight.

Question 20

Difference between continuous and discontinuous variation?

Answer 20

Continuous:
- Shows a range of values.
- Caused by an interaction between genetics and environment.

Discontinuous:
- Distinct categories where individuals belong to specific groups.
- Solely caused by genetic factors. Environment has no effect.
- Different genes have different effects on the phenotype. Different alleles at a single gene locus have a large effect on the phenotype.

Question 21

Define adaptation.

Answer 21

A characteristics that aids an organism’s survival in its environment.

Question 22

Describe the 3 types of adaptation.

Answer 22

Anatomical - physical features of an organism. E.g. the white fur of a polar bear provides camouflage in the snow so it has less chance of being detected by prey. Wings, scales.

Physiological - biological processes within an organism. Mosquitos produce chemicals that stops host’s blood from clotting when they bite so that they can feed more easily. Snakes producing venom. Water holding.

Behavioural - the way an organism behaves. E.g. reptiles bask in the sun to absorb heat.

Question 23

State the difference between analogous and homologous structures.

Answer 23

Analogous structures are structures that have adapted to perform the same function but have a different origin whereas homologous structures appear superficially different but have the same underlying structure.

Question 24

What is convergent evolution?

Answer 24

Organisms from different taxonomic groups may show similar adaptations even though they do not share a recent common ancestor. Shared adaptations between unrelated organisms arise due to convergent evolution:

=> Two species live in different parts of the world with similar environments

the species deal with the same selection pressures

the same characteristics are advantageous in the two environments, so individuals with these characteristics are more likely to survive and reproduce

over time the advantageous characteristics become widespread in both populations

Organisms displaying convergent evolution have analogous structures – anatomical features that perform the same function in different organisms, but have a different origin.

Question 25

Genetic variation.

Answer 25

These differences in DNA base sequences between individual organisms within a species population are called genetic variation. Genetic variation is transferred from one generation to the next and results in genetic diversity within a species. Selection pressures increase the chance of individuals with a specific (more advantageous) phenotype surviving and reproducing over other. The individuals with the favoured phenotypes are described as having a higher fitness. The fitness of an organism is defined as its ability to survive and pass on its alleles to offspring. Organisms with higher fitness possess adaptations that make them better suited to their environment. A population with a large gene pool or high genetic diversity has a strong ability to adapt to change. If a population has a small gene pool or very low genetic diversity then they are much less able to adapt to changes in the environment and so can become vulnerable to extinction

Answer 26

Environmental factors affect the chance of survival of an organism - they act as a selection pressure Every individual within a species population has the potential to reproduce and have offspring which contribute to population growth If all the offspring of every individual survived to adulthood and reproduced, the population would experience exponential growth This type of growth only happens when there are no environmental factors or population checks acting on the population (for example, when there are plentiful resources and no disease) One well known but rare example of exponential growth in a population is the introduction of 24 European rabbits into Australia in the 1800s. The rabbits had an abundance of resources, little or no competition and no natural predators. This meant the population increased rapidly and they became a major pest In reality, there are several environmental factors that prevent every individual in a population making it to adulthood and reproducing.

Question 27

State 3 selection pressures that a plant may experience.

Answer 27

availability of light / water / nutrients / carbon dioxide / space, risk of being eaten, disease.

Question 28

Natural selection.

Answer 28

Random mutation can produce new alleles of a gene. Many mutations are harmful or neutral but, under certain environmental conditions, the new alleles may benefit their possessor, leading to an increased chance of survival and increased reproductive success. The advantageous allele is passed onto the next generation. As a result, over several generations, the new allele will increase in frequency in the population. Summary: Variations exist within a population (1); those with the best characteristics survive AND reproduce (1); characteristics are passed onto their offspring through genes (1). A mutation occurred / existed in the mosquitos DNA which made them DDT resistant (1) these organisms survived exposure to DDT and reproduced (1); mutation which caused resistance is passed onto their offspring (1); frequency of the DDT-resistant allele increases in the population.

Question 29

2 ways which bacteria inherit antibiotic resistance?

Answer 29

Vertical transmission: bacteria reproduce asexually by binary fission. If one bacterium contains a mutant gene that gives it antibiotic resistance, all of its descendants (millions of which can be produced in a matter of hours) will also have the antibiotic resistance. This form of transmission enables antibiotic resistance to spread within a bacterial population. Horizontal transmission: Plasmids (the small rings of DNA present in bacterial cells) often contain antibiotic-resistant genes. These plasmids are frequently transferred between bacteria (even from one species to another). This occurs during conjugation (when a thin tube forms between two bacteria to allow the exchange of DNA) – DNA from the bacterial chromosome can also be transferred in this way. In this way, a bacterium containing a mutant gene that gives it antibiotic resistance could pass this gene on to other bacteria (even those from a different species). This is how ‘superbugs’ with multiple resistance have developed (e.g. methicillin-resistant Staphylococcus aureus – MRSA). This form of transmission enables antibiotic resistance to spread within or between bacterial populations.

Question 30

Consequences of pesticide resistance?

Answer 30

A problem for food security. So farmer are encouraged to use other forms of insect pest control, such as: => Biological control (introducing a natural parasite or predator of the pest). => Using crops that have been genetically modified to be pest-resistant.