Module 4: Classification and evolution Flashcards
List the ranks of the taxonomic classification system.
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What are the 3 domains?
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 (prokaryotes) - first discovered in extreme environments. No nucleus, no murein cell walls, similar size to bacteria, rRNA is more similar to eukaryotes.
Both Archaea and Bacteria possess 70S ribosomes
The 70S ribosomes in Archaea possess a smaller subunit that is more similar to the subunit found in Eukaryotic ribosomes than subunits in Bacterial 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
What are the 5 kingdoms?
Animalia, Plantae, Fungi, Protoctista, Prokaryota
Explain each of the 5 kingdoms.
Animalia - multicellular, small temporary vacuole, heterotrophic.
Plantae - multicellular, cell wall, large permanent vacuole, autotrophic.
Fungi - unicellular (?), cell wall, large permanent vacuole, heterotrophic.
Protoctista - multicellular and unicellular, some have cell walls, some have vacuoles, auto and heterotrophic.
Prokaryota - mostly unicellular, cell wall, some have vacuoles, auto and heterotrophic.
Classification table for wolf?
Domain = Eukarya
Kingdom = Animalia
Phylum = Chordata
Class = Mammalia
Order = Carnivora
Family = Canidae
Genus = Canis
Species = lupus
Define species.
Organism that can reproduce to produce fertile offspring.
The binomial name for a species is always …
Underlined when handwritten, italics when typed. It consists of the genus and species name.
Define phylogeny.
The evolutionary history of 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.
Fossil evidence for the theory of evolution by natural selection (passing on advantageous alleles).
Fossils are preserved remains of organisms or other features left by organisms, such as footprints, burrows and faeces
We can tell from fossils that environments (and the organisms living in these environments) have changed significantly over millions of years
Fossils, as well as the rocks they are found in, can be dated, allowing us to accurately put fossil organisms into a sequence from oldest to youngest (i.e to see how the organisms changed through evolutionary time)
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
All this has provided evidence for the gradual change from simple life forms, such as Archaea and Bacteria, to complex Eukaryotic life forms and the evolutionary relationships between organisms
Molecular evidence for the theory of evolution by natural selection.
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.
Difference between interspecific and intraspecific variation?
Interspecific - variation between individuals of different species.
Intraspecific - variation between individuals of the same species.
Difference between continuous and discontinuous variation?
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.
Define adaptation.
A characteristics that aids an organism’s survival in its environment.
Describe the 3 types of adaptation.
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.
Physiological - biological processes within an organism. Mosquitos produce chemicals that stoa host’s blood from clotting when they bite so that they can feed more easily.
Behavioural - the way an organism behaves. E.g. reptiles bask in he sun to absorb heat.
What is convergent evolution?
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
Convergent evolution occurs by natural selection as follows:
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
Genetic variation.
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
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.
Natural selection.
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.
2 ways which bacteria inherit antibiotic resistance?
Vertical transmission: Bacteria reproduce asexually by binary fission (the DNA of the bacterial chromosome is replicated and the bacterial cell divides in two, with each daughter cell receiving a copy of the chromosome). Bacteria reproduce like this very rapidly (on average, every 20 minutes). 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.
Antibiotic resistance in bacteria is an example of natural selection that humans have helped to develop. This is due to the overuse of antibiotics in situations where they were not really necessary or the incorrect use of antibiotics, for example:
Overuse of antibiotics and antibiotics being prescribed when not necessary
Large scale use of antibiotics in farming to prevent disease when livestock are kept in close quarters, even when animals are not sick.
For treatment of non-serious infections
Routine treatment of animals in agriculture
Failure to finish the prescribed course of antibiotics
A variety of steps can be taken to reduce cases of antibiotic resistance, including:
Only prescribing antibiotics when absolutely necessary
Ensure patients complete courses of antibiotics
Rotate which antibiotics are used so that one type is not continuously used in the treatment of a specific disease
Hold back some antibiotics from being used at all so they are available as a ‘last resort’
More investment in research into new antibiotics
PEST RESISTANCE - Pesticides are chemicals that kill pests of any kind, including insect pests, pathogenic organisms or weeds
There are various types of pesticides, including:
Insecticides (kill insect pests)
Herbicides (kill plant pests)
Fungicides (kill fungal pests)
Molluscicides (kill slug and snail pests)
Rodenticides (kill rodent pests)
A major global use of pesticides is in the control of insect pests that consume or otherwise damage human food crops (e.g. Colorado beetles that eat potato crops) or insects that are vectors of disease (e.g. Anopheles mosquitos that transmit malaria)
In a similar way to antibiotic resistance in bacteria, insecticides that are sprayed on crops act as selective agents
A selective agent is any environmental factor that influences the survival of a particular species and so drives natural selection in that species
For example, any insect that has a mutation making them resistant to the insecticide will survive and reproduce, passing on the resistant gene
Consequences of antibiotic resistance?
By using antibiotics frequently, humans exert a selective pressure on the bacteria, which supports the evolution of antibiotic resistance. Scientists are trying hard to find new antibiotics that bacteria have not yet been exposed to, but this process is expensive and time-consuming. Some strains of bacteria can be resistant to multiple antibiotics and they create infections and diseases which are very difficult to treat.
Tighter controls in countries in which antibiotics are sold without a doctor’s prescription
Doctors avoiding the overuse of antibiotics, prescribing them only when needed (patients must only be given antibiotics when absolutely essential) – doctors should test the bacteria first to make sure that they prescribe the correct antibiotic
Antibiotics not being used in non-serious infections that the immune system will ‘clear up’ (patients must not keep unused antibiotics for self-medication of such non-serious infections in the future)
When prescribed a course of antibiotics, the patient finishing the entire course (even if they feel better after a few days) so that all the bacteria are killed, and none are left to mutate to become resistant strains
Antibiotics not being used for viral infections (antibiotics have no effect on viruses anyway, and this just provides an unnecessary chance for bacteria to develop resistance)
Consequences of pesticide resistance?
a problem for the security of future food supplies for human populations, especially those that already face food shortages
Again, in a similar way to the use of antibiotics against bacteria, insecticides should be used sparingly or on rotation to avoid the evolution of resistance in pest insect populations
Using a combination of pesticides can delay the emergence and spread of resistance in pest insect populations
Farmers are also encouraged to use other forms of insect pest control, such as:
Biological control (introducing a natural parasite or predator of the pest insect)
Using crops that have been selectively bred or genetically modified to be pest-resistant.
