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What are the five kingdoms?
- Prokaryotes (prokaryotae)
- Protoctists (protoctista)
- Plants (plantae)
- Animals (animalia)
Outline the characteristics of prokaryotes.
- Have no nucleus
- loop of naked DNA (not associated with histone proteins, not arranged in linear chromosomes)
- no membrane-bound organelles
- smaller ribosomes
- respiration not in mitochondria but in membrane systems
- cells smaller than eukaryotes
- may be free-living or parasitic; some cause disease
Outline characteristics of Protoctists.
- mostly single-celled
- show a wide variety of forms
- various plant-like or animal-like features
- mostly free-living
- autotrophic or heterotrophic nutrition
- One thing common is that they do not qualify to be in the other 4 kingdoms!
Outline the characteristics of fungi.
- have mycelium, which consists of hyphae
- have walls made of chitin
- cytoplasm that is multinucleate (many nuclei)
- mostly free-living and saprophytic - cause decay of organic matter
Outline characteristics of plants.
- cells surrounded by cellulose cell wall
- produce multicellular embryos from fertilised eggs
- autotrophic nutrition (photosynthesise)
Outline the characteristics of animals.
- heterotrophic nutrition
- have fertilised eggs that develop into ball of cells called blastula
- usually able to move around
List the taxonomic hierarchy (the 8 taxa) in order.
Why is the binomial system used instead of common names?
Simply because it avoids potential confusion caused by using common names (like different languages etc)
Outline the binomial system of naming living organisms.
- 2 names - Genus name and species name
- Genus name always given a capital first letter
- species name is lower case first letter
- The binomial Latin name is written in a style that makes it stand out - italics in printed text and underlined in handwritten text.
- eg. Homo sapiens
Give one importance of identifying organisms.
During environmental impact assessment (EIA), scientists need to know what species are present in that area. If a species is very rare, then losing that habitat would have a major impact on species and environment. It is important to identify species in order to know whether they are endangered etc.
What is a dichotomous key?
- Uses a series of questions with two alternative answers to help you identify a specimen.
- (You need to be able to use it)
We can use biochemistry in classification. Give one example.
- The protein cytochrome c is found in all organisms (except prokaryotes) and is used in respiration.
- By studying the proteins, and comparing the differences in amino acid sequence, we can see how closely one organism is related to another.
- If the sequences are the same - two species must be closely related
- The more different, the less closely related
Except from using some proteins, what is perhaps the most accurate way of using biochemistry in classification?
Examining how similar DNA or RNA is in two species. The more they are the same, the more closely those two are related.
Recently, the three domains was introduced. Why? What molecular evidence?
- Prokaryote was divided into 2 groups - Bacteria and Archaeae. Because Bacteria are fundamentally different from Archaeae and Eukaryotae.
- eg. different enzymes (RNA polymerase) for buidling RNA
- Archaeae more similar to Eukaryotae than Bacteria.
- (NEED TO ASK TEACHER DON'T QUITE UNDERSTAND)
What is variation?
The presence of differences between individuals, within and between species.
What are the two forms of variation?
What is continuous variation?
- Variation in which there is a full range of intermediate phenotypes between two extremes.
- eg. human height, length of leaves on oak tree
What is discontinuous variation?
- Variation in which there are discrete groups of phenotypes with no or very few individuals in between.
- eg. sex (plants can be male, female or hermaphrodite); presence/absence of flagella; human blood groups
What causes variation?
- Inherited genetic variation: combination of alleles inherited by parents
- Environmental causes: eg. skin will tan with more sunlight. Can affect direction and amount of grouth.
What is an adaptation?
Feature/ variation that enhances the survival and long-term reproductive success of the organism.
A well adapted organism will be able to:
- find enough food or photosynthesise well
- find enough water
- gather enough nutrients
- defend itself (from predators and disease)
- survive physical conditions of environment (eg. temp)
- respond to changes in environment
- able to reproduce successfully
What are the three types of adaptation?
- Behavioural adaptations - eg. work withdrawal when being touched.
- Physiological/biochemical - ensures correct functioning of cell processes eg. producing correct enzymes to respire sugars present in environment
- Anatomical (structural) - eg. flagella in bacteria
Give an example of organism that is adapted to its environment.
- Xerophytic plants
- Behavioural: close stomata when little water is available, rolling up leaves
- Physiological: mechanisms by which plant can open/close stomata - eg. guard cells
- Anatomical: small leaves, very waxy leaves, hairy leaves and pits.
List the 4 particular observations Charles Darwin listed in proposing his theory of natural selection.
- Offspring generally appears similar to their parents
- No two individuals are identical
- Organisms have the ability to produce large numbers of offspring
- Populations in nature tend to remain fairly stable in size
What were Charles Darwin's conclusions?
- There is a struggle to survive
- Better adapted individuals survive and pass on their characteristics
- Over time, a number of changes may give rise to a new species
What is speciation?
The formation of a new species from a pre-existing one.
In order for speciation to occur, there must be some _________ _____.
Give 2 reproductive barriers:
- Geographical separation - known as allopatric speciation
- Any change - biochemical, behavioural, that prevents one member of population from breeding with another. sympatric separation.
How can fossils be evidence for the theory of evolution?
- Shows how world was inhabited by species that were different from those present today.
- Old species have died out
- New species have arisen
- New species that appear are often similar to older ones found in same place.
- Fossils from more recent times show more similarities, whereas older ones are more different.
How can biological molecules be used as evidence for evolution?
- Fact that certain molecules found throughout living world shows how it came from one ancestor
- Two closely related species have similar/identical biological molecules
- Opposite for distantly related species
- Evidence from molecules like cytochrome c & other proteins.
What are the 3 major components of evolution?
Remember, individuals do not evolve.
Individuals are selected, and the population evolves.
How could resistance to insecticides develop? (individual traits that are resistant to insecticides?)
- Insects may be able to break them down (using enzymes) - they metabolise them
- Target receptor protein on cell membrane may be modified.
Explain why evolution occurs in a shorter time in populations of microorganisms than in mammals.
Because microorganisms have a much shorter life cycle. More generations pass in a quicker time, and this means more mutations and variations. More variations mean more potential adaptations.