2.1: Classification and biodiversity
There are two types of classification, phylogenetic and taxonomic.
This is grouping based on physical characteristics, with a hierarchical structure of eight levels known as taxa (taxon for singular.)
An example of the classification of a tiger is below:
Taxon | Tiger example |
|---|---|
Domain | Eukaryota |
Kingdom | Animalia |
Phylum | Chordata |
Class | Mammalia |
Order | Primates |
Family | Hominidae |
Genus | Homo |
Species | Sapien |
It is known as discrete data, as there is no cross over between the groups.
It is also tentative, meaning it is subject to change. This usually happens due to scientific advancement, such as DNA testing.
Scientific names are derived from this ranking, and are known as binomial names.
They were invented by Carlos Linnaeus in the 18th century, and use Latin.
This system of naming has many rules:
The names come from the bottom two categories, genus and species.
Genus is capitalised, species is not.
First time of the name appearing it must be written in full, then can be written with an abbreviation, for example P.Tigris.
If it is typed, it must be typed in italics. Often in handwriting it is underlined.
There are three domains:
Eukaryota - these are organisms with eukaryotic cells, such as plants, animals and fungi.
Archaea - ancient bacteria with unusual metabolisms. Many are extremophiles, meaning they live in extreme conditions for humans such as high temperatures, lack of oxygen, high pressure and low pH.
Eubacteria - familiar bacteria, such as E.coli and salmonella.
There are five kingdoms, four for eukaryota and one for archaea and eubacteria.
Eukaryota are:
Protista - these can be multi or single celled organisms, and may have animal or plant like cells, or both. They can have chloroplasts, vacuoles, cellulose cell walls and can be autotrophic or heterotrophic.
Plantae - these can reproduce via seeds or spores, based on whether they are flowering or not. They are multicellular, have permanent vacuoles, cellulose cell walls and are autotrophic.
Fungi - can be single celled or hyphal, meaning the fungi are connected through branches. They have permanent vacuoles, chitin cell walls and can be either saprotrophic or parasitic.
Animalia - multicellular, with temporary small vacuoles, no cell wall and are heterotrophic.
Archaea and eubacteria are:
Prokaryotic - microscopic, single-celled, some have mesosomes and photosynthetic lamellae, peptidoglycan cell walls and can be parasitic, saprotrophic or autotrophic.
While the names and orders of the other taxons are needed in the exam, the different groups and examples are not.
However, an important phylum to know is chordata, which means they have a backbone.
This form of classification is based on evolutionary links between species.
This is shown through phylogenetic trees, or cladograms, which shown a family’s evolutionary history over time.
They are linked with branches, with each split representing the last common ancestor a species shared.
Relatedness between organisms determines how many common features they have.
The closer they are related, the most similar traits they will have.
Evolution suggests that all animals, no matter how distantly connected, have a common ancestor.
LUCA stands for last universal common ancestor, and existed 4.5 billion years ago.
One type of similar structures are homologous structure, which are structures with a similar origin but a different function.
For example, pentadactyl limbs are in multiple vertebrate, including birds, fish and mammals. However, they are used for wings, fins and hands with purposes such as swimming, flying and grabbing.
This is an example of divergent evolution, where organisms with similar origins evolve to have different traits.
The other type of similar structures is analogous structures, which are structures with a different origin but the same function.
For example, sharks, penguins and dolphins all developed fins for swimming, even though their most recent common ancestor didn’t have fins.
This is an example of convergent evolution, where organisms with different origins evolve similar traits.
There are four methods of checking relationships between species:
DNA sequences:
Comparing the base sequences of DNA, as base sequences alter slightly over the course of evolution.
The more similarities = The more closely related.
DNA hybridisation:
DNA is taken from two different species, the strands separated and cut into fragments.
The two fragments are mixed and hybridise where they have complementary base sequences.
The more hybridisation = The more closely related.
Amino acid sequences:
Comparing the amino acid sequences of two species for the same protein, as these sequences change over time through evolution.
The more similarities = The more closely related.
Immunology:
By mixing the antigens (a substance that allows immune systems to identify it, in this case a coating on the outside of a cell) of one species with the antibodies of another, they coagulate if they do not identify the antigen as a foreign body/threat.
The more coagulation = The more closely related.
Biodiversity is the number of species (known as species richness) and the number of organisms in each species (known as species evenness).
Biodiversity is not consistent, and vary across environments.
Bright environments have higher biodiversity, as the sunlight provides more energy for plants to grow and therefore more energy for carnivores to consume.
More energy flowing through an ecosystem produces more species and individual organisms, meaning locations near the equator have more biodiversity than polar regions.
Biodiversity hotspots are areas of high biodiversity, and these cluster around the equator and tropics, due to high light intensity and therefore high energy input into ecosystems.
Succession:
Communities of organism change their habitat over time, making it more suitable for other species.
This change in community composition is known as succession, and increases animal biodiversity but decreases plant biodiversity.
Natural selection:
This is the process of evolution that occurs in six steps:
Mutation - Changes in DNA.
Variation - A difference in biochemical function, outward appearance or behaviour occurs.
Competitive advantage - Some are more suited to the environment than others and out-compete members of their own and other species.
Survival of the fittest - Those more suited to the environment survive better.
Reproduction - They are then more likely to reproduce as they survive to maturity.
Pass on - The offspring inherit the advantageous alleles, so they are more suited to the environment.
Continuation - These offspring outperform their competitors and have more children, until eventually this trait becomes the norm.
Natural selection generates biodiversity, as it helps animals adapt to changes such as a higher temperature environment.
In some situations, biodiversity can be decreased by natural selection, such as when a meteor killed the dinosaurs.
Human influence:
Human activity has decreased biodiversity in many ways:
In tropical rainforests, such as Brazil, farming, roads and industry destroy habitats and reduced the number of animals in an area. This has led to extinction in some cases.
Over-fishing has depleted fish and stressed out areas such as coral reefs. Trawlers dredging the ocean floor disrupt environments and damage populations of fish, sea mammals and invertebrates.
Misuse of land, such as cattle trampling, and rises in temperature have increased the area of deserts, such as the Sahara.
Rivers are polluted by industrial chemicals, for example the baiji (Yangtze River dolphin) was declared extinct in 2006 due to this and other human factors.
It has also increased biodiversity:
In London, due to the River Thames being so polluted it produced a terrible odour and everything in it was dead. After this, sewers were built and the river recovered. After this, salmon, sea horses, heron, dolphins and a seal have been spotted in the river.
Biodiversity is necessary for human civilisation:
A small number of plant species provide our staple foods, such as wheat and rice, for people worldwide.
Medicinal drugs are derived from plants and fungi, such as aspirin and antibiotics.
Living organisms provide important raw materials, such as rubber and cotton.
They can also provide in future:
New medicines.
New foods.
Humans also have a obligation to protect the uniqueness of each species and environments, as it is valuable.
This is done by counting the amount of species in an area, usually using a quadrat.
n stands for the number of organisms in singular species and N stands for the entire number of organisms.
Species | Number of individuals | n-1 | n(n-1) |
|---|---|---|---|
Flatworm | 11 | 11-1=10 | 10x11=110 |
Freshwater shrimp | 55 | 55-1=54 | 54x55=2970 |
Blackfly larva | 1 | 1-1=0 | 0x1=0 |
Caddis fly larva | 1 | 1-1=0 | 0x1=0 |
Mayfly nymph | 7 | 7-1=6 | 6x7=42 |
Midge pupa | 1 | 1-1=0 | 0x1=0 |
Stonefly nymph | 4 | 4-1=3 | 3x4=12 |
N=8 | =3134 |
1-3134÷80(80-1)=1-3134÷6320=1-0.4959=0.5(2dp)
The highest number possible is one.
Also known as the capture-recapture technique, which involves capturing and marking animals and then releasing them back into the environment, and then recapturing and counting the amount who were marked.
A stands for number in the second sample, n stands for number of first sample and a stands for the number who were marked in the second sample.
Tree type | First sample | Second sample | Number marked in second sample | Axn÷a |
|---|---|---|---|---|
Beech | 14 | 27 | 6 | 53.6 |
Oak | 8 | 17 | 3 | 32 |
Examining genes and alleles of species shows the variation within a species:
A gene’s position on the chromosome is called the locus, and this shows polymorphism if it has two or more alleles and the rarest ones occurring more than could be attributed to mutation alone.
The more different alleles a gene has = higher polymorphism.
The more proportionate the alleles are to each other, for example all of them occurring in 20% of the gene pool, the more polymorphism.
More proportionate the percentages of alleles in the gene pool = higher biodiversity.
DNA fingerprinting is the process of comparing the DNA/genetic profiles/fingerprints to see how biodiverse the DNA of a species is, by comparing the number and position of the DNA bands.
If only one base differs, this is known as a SNP (single nucleotide polymorphisms).
Regions of DNA that vary can be 20-40 base pairings long and can be repeated many times. They are known as HVRs (hyper-variable regions) or STRs (short tandem repeats).
When natural selection causes the trait to become more common, it is called adaptation.
The useful trait is known as an ‘adaptive trait‘.
Traits which animals are born with, such as:
Dolphins having streamlined bodies allowing them to swim faster.
Beelines on plants that indicate where the honey or nectar is to attract as many pollinators as possible.
Traits which are reversible chemical reactions, such as:
Mammals which hibernate to maintain their body temperature.
Leaves falling off deciduous plants to stop dehydration throughout winter.
Traits that change an organisms behaviour, such as:
Plants flowering in spring so they can pollinate.
Mating rituals.
Migration.
There are two types of classification, phylogenetic and taxonomic.
This is grouping based on physical characteristics, with a hierarchical structure of eight levels known as taxa (taxon for singular.)
An example of the classification of a tiger is below:
Taxon | Tiger example |
|---|---|
Domain | Eukaryota |
Kingdom | Animalia |
Phylum | Chordata |
Class | Mammalia |
Order | Primates |
Family | Hominidae |
Genus | Homo |
Species | Sapien |
It is known as discrete data, as there is no cross over between the groups.
It is also tentative, meaning it is subject to change. This usually happens due to scientific advancement, such as DNA testing.
Scientific names are derived from this ranking, and are known as binomial names.
They were invented by Carlos Linnaeus in the 18th century, and use Latin.
This system of naming has many rules:
The names come from the bottom two categories, genus and species.
Genus is capitalised, species is not.
First time of the name appearing it must be written in full, then can be written with an abbreviation, for example P.Tigris.
If it is typed, it must be typed in italics. Often in handwriting it is underlined.
There are three domains:
Eukaryota - these are organisms with eukaryotic cells, such as plants, animals and fungi.
Archaea - ancient bacteria with unusual metabolisms. Many are extremophiles, meaning they live in extreme conditions for humans such as high temperatures, lack of oxygen, high pressure and low pH.
Eubacteria - familiar bacteria, such as E.coli and salmonella.
There are five kingdoms, four for eukaryota and one for archaea and eubacteria.
Eukaryota are:
Protista - these can be multi or single celled organisms, and may have animal or plant like cells, or both. They can have chloroplasts, vacuoles, cellulose cell walls and can be autotrophic or heterotrophic.
Plantae - these can reproduce via seeds or spores, based on whether they are flowering or not. They are multicellular, have permanent vacuoles, cellulose cell walls and are autotrophic.
Fungi - can be single celled or hyphal, meaning the fungi are connected through branches. They have permanent vacuoles, chitin cell walls and can be either saprotrophic or parasitic.
Animalia - multicellular, with temporary small vacuoles, no cell wall and are heterotrophic.
Archaea and eubacteria are:
Prokaryotic - microscopic, single-celled, some have mesosomes and photosynthetic lamellae, peptidoglycan cell walls and can be parasitic, saprotrophic or autotrophic.
While the names and orders of the other taxons are needed in the exam, the different groups and examples are not.
However, an important phylum to know is chordata, which means they have a backbone.
This form of classification is based on evolutionary links between species.
This is shown through phylogenetic trees, or cladograms, which shown a family’s evolutionary history over time.
They are linked with branches, with each split representing the last common ancestor a species shared.
Relatedness between organisms determines how many common features they have.
The closer they are related, the most similar traits they will have.
Evolution suggests that all animals, no matter how distantly connected, have a common ancestor.
LUCA stands for last universal common ancestor, and existed 4.5 billion years ago.
One type of similar structures are homologous structure, which are structures with a similar origin but a different function.
For example, pentadactyl limbs are in multiple vertebrate, including birds, fish and mammals. However, they are used for wings, fins and hands with purposes such as swimming, flying and grabbing.
This is an example of divergent evolution, where organisms with similar origins evolve to have different traits.
The other type of similar structures is analogous structures, which are structures with a different origin but the same function.
For example, sharks, penguins and dolphins all developed fins for swimming, even though their most recent common ancestor didn’t have fins.
This is an example of convergent evolution, where organisms with different origins evolve similar traits.
There are four methods of checking relationships between species:
DNA sequences:
Comparing the base sequences of DNA, as base sequences alter slightly over the course of evolution.
The more similarities = The more closely related.
DNA hybridisation:
DNA is taken from two different species, the strands separated and cut into fragments.
The two fragments are mixed and hybridise where they have complementary base sequences.
The more hybridisation = The more closely related.
Amino acid sequences:
Comparing the amino acid sequences of two species for the same protein, as these sequences change over time through evolution.
The more similarities = The more closely related.
Immunology:
By mixing the antigens (a substance that allows immune systems to identify it, in this case a coating on the outside of a cell) of one species with the antibodies of another, they coagulate if they do not identify the antigen as a foreign body/threat.
The more coagulation = The more closely related.
Biodiversity is the number of species (known as species richness) and the number of organisms in each species (known as species evenness).
Biodiversity is not consistent, and vary across environments.
Bright environments have higher biodiversity, as the sunlight provides more energy for plants to grow and therefore more energy for carnivores to consume.
More energy flowing through an ecosystem produces more species and individual organisms, meaning locations near the equator have more biodiversity than polar regions.
Biodiversity hotspots are areas of high biodiversity, and these cluster around the equator and tropics, due to high light intensity and therefore high energy input into ecosystems.
Succession:
Communities of organism change their habitat over time, making it more suitable for other species.
This change in community composition is known as succession, and increases animal biodiversity but decreases plant biodiversity.
Natural selection:
This is the process of evolution that occurs in six steps:
Mutation - Changes in DNA.
Variation - A difference in biochemical function, outward appearance or behaviour occurs.
Competitive advantage - Some are more suited to the environment than others and out-compete members of their own and other species.
Survival of the fittest - Those more suited to the environment survive better.
Reproduction - They are then more likely to reproduce as they survive to maturity.
Pass on - The offspring inherit the advantageous alleles, so they are more suited to the environment.
Continuation - These offspring outperform their competitors and have more children, until eventually this trait becomes the norm.
Natural selection generates biodiversity, as it helps animals adapt to changes such as a higher temperature environment.
In some situations, biodiversity can be decreased by natural selection, such as when a meteor killed the dinosaurs.
Human influence:
Human activity has decreased biodiversity in many ways:
In tropical rainforests, such as Brazil, farming, roads and industry destroy habitats and reduced the number of animals in an area. This has led to extinction in some cases.
Over-fishing has depleted fish and stressed out areas such as coral reefs. Trawlers dredging the ocean floor disrupt environments and damage populations of fish, sea mammals and invertebrates.
Misuse of land, such as cattle trampling, and rises in temperature have increased the area of deserts, such as the Sahara.
Rivers are polluted by industrial chemicals, for example the baiji (Yangtze River dolphin) was declared extinct in 2006 due to this and other human factors.
It has also increased biodiversity:
In London, due to the River Thames being so polluted it produced a terrible odour and everything in it was dead. After this, sewers were built and the river recovered. After this, salmon, sea horses, heron, dolphins and a seal have been spotted in the river.
Biodiversity is necessary for human civilisation:
A small number of plant species provide our staple foods, such as wheat and rice, for people worldwide.
Medicinal drugs are derived from plants and fungi, such as aspirin and antibiotics.
Living organisms provide important raw materials, such as rubber and cotton.
They can also provide in future:
New medicines.
New foods.
Humans also have a obligation to protect the uniqueness of each species and environments, as it is valuable.
This is done by counting the amount of species in an area, usually using a quadrat.
n stands for the number of organisms in singular species and N stands for the entire number of organisms.
Species | Number of individuals | n-1 | n(n-1) |
|---|---|---|---|
Flatworm | 11 | 11-1=10 | 10x11=110 |
Freshwater shrimp | 55 | 55-1=54 | 54x55=2970 |
Blackfly larva | 1 | 1-1=0 | 0x1=0 |
Caddis fly larva | 1 | 1-1=0 | 0x1=0 |
Mayfly nymph | 7 | 7-1=6 | 6x7=42 |
Midge pupa | 1 | 1-1=0 | 0x1=0 |
Stonefly nymph | 4 | 4-1=3 | 3x4=12 |
N=8 | =3134 |
1-3134÷80(80-1)=1-3134÷6320=1-0.4959=0.5(2dp)
The highest number possible is one.
Also known as the capture-recapture technique, which involves capturing and marking animals and then releasing them back into the environment, and then recapturing and counting the amount who were marked.
A stands for number in the second sample, n stands for number of first sample and a stands for the number who were marked in the second sample.
Tree type | First sample | Second sample | Number marked in second sample | Axn÷a |
|---|---|---|---|---|
Beech | 14 | 27 | 6 | 53.6 |
Oak | 8 | 17 | 3 | 32 |
Examining genes and alleles of species shows the variation within a species:
A gene’s position on the chromosome is called the locus, and this shows polymorphism if it has two or more alleles and the rarest ones occurring more than could be attributed to mutation alone.
The more different alleles a gene has = higher polymorphism.
The more proportionate the alleles are to each other, for example all of them occurring in 20% of the gene pool, the more polymorphism.
More proportionate the percentages of alleles in the gene pool = higher biodiversity.
DNA fingerprinting is the process of comparing the DNA/genetic profiles/fingerprints to see how biodiverse the DNA of a species is, by comparing the number and position of the DNA bands.
If only one base differs, this is known as a SNP (single nucleotide polymorphisms).
Regions of DNA that vary can be 20-40 base pairings long and can be repeated many times. They are known as HVRs (hyper-variable regions) or STRs (short tandem repeats).
When natural selection causes the trait to become more common, it is called adaptation.
The useful trait is known as an ‘adaptive trait‘.
Traits which animals are born with, such as:
Dolphins having streamlined bodies allowing them to swim faster.
Beelines on plants that indicate where the honey or nectar is to attract as many pollinators as possible.
Traits which are reversible chemical reactions, such as:
Mammals which hibernate to maintain their body temperature.
Leaves falling off deciduous plants to stop dehydration throughout winter.
Traits that change an organisms behaviour, such as:
Plants flowering in spring so they can pollinate.
Mating rituals.
Migration.
