A3.1 Diversity of Organisms

What is an organism?

An individual plant, animal, bacterium or any living thing

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

The difference between organisms e.g.

1. Visual appearances - fur colour and body length

2. Behaviour - mating rituals or levels of aggression

3. Biochemistry - antibiotic resistance or metabolic products

What are patterns of variation used for?

They are the basis of naming and classifying organisms

Are any two individuals identical?

No - there are even variations between members of the same species

Is there more variation between members or the same of different species?

Different species

What is variation the result of?

Both genetic and environmental factors

What do genes do?

They determine which proteins an organism can produce

How is genetic variation generated?

When mutations occur or different combinations of alleles during sexual reproduction

What does the term ‘species’ mean?

It is the term used for a group of organisms with shared traits and is how species have been named and classified

When was is developed?

17th century by biologists

What is the Morphological concept?

That a species is a group of organisms with a characteristic outward form and inner structure (size, shape, and body structure) - expectation that there is clear differences in the structure of all species

Who invented it?

Carl Linnaeus

Give an example of the Morphological concept

Mice of similar traits, from different countries, that have similar traits and are considered to be part of the same species, despite being unable to breed with each other.

Why system is used to give a species a scientific name?

Binomial system

What are the two parts of a scientific name using the binomial system?

The Genus (the first part of the name) and the species (the second part)

What has a capital letter?

Genus

e.g. what is the scientific name for humans?

Homo sapiens

What is the second way of classifying species?

Biological species concept

What is the biological species concept?

A species is a group of organisms that can successfully interbreed and produce fertile offspring

What does interbreeding allow?

Members of a species to share genes in a gene pool so they share many traits

What are the 3 limitations of the Biologicals species concept?

1. Asexual reproduction

2. Fertile hybrids

3. Extinction

Why is asexual reproduction a limitation?

Asexually reproducing organisms don’t interbreed, meaning their offspring is considered a new species according to the biological concept (more detail later)

Fertile hybrid limitations?

On rare occasions, animals of difference species can breed and produce fertile offspring. According to the concept, the offspring should be a new species, but according to scientists, for it to be a new species it needs to be a regular occurrence.

Extinction limitation?

If the animal is extinct, it is not possible to breed them so how do we know what species they belong to e.g. Woolly mammoths and elephants

What is speciation

Splitting of one population into two

How can this happen?

Natural selection or genetic drift

If a population lives in 2 different places and their traits diverge over time to adapt to their environment

Is this process immediate or gradual?

Gradual - over thousands of years

Is it east or hard for taxonomists to classify organisms into species?

Sometimes very hard as the accumulation of differences between the populations happens over a variety of times (negligible to rapid)

What is the decision regarded as?

Arbitrary

What is a characteristic feature of members of a species?

Number of chromosomes

What chromosome number is given to a species?

diploid number

Is it odd or even?

even

How many chromosomes do humans have?

46

How many chromosomes do chimpanzees have?

48

What is a karyotype?

The number and type of chromosomes in a cell or organism

What is a karyogram?

Photos and diagrams where chromosomes of an organism are shows in homologous pairs of decreasing length

What stage must a cell be in to prepare a karyogram?

Metaphase of mitosis where they are examined microscopically

Can the cells be overlapping?

No

They are digitally classified into homologous pairs using what 3 things?

1. Stains

2. Chromosome sizes

3. Centromere

How are stains used?

They give chromosomes distinct patters with different bonding patterns, with different bonding in each type of homologous chromosome.

How are chromosome sizes used?

The sizes vary between chromosomes but each chromosome pair is approximately the same length

How s the centromere used?

Each chromosome has a centromere where there is a constriction of the chromatids. Its position is the same in a chromosome pair and can be anywhere from the middle to the ends

What is the hypothesis involving our chromosome 2?

Humans = 46, Chimpanzees = 48

That million of years ago, our ancestors had 48 chromosomes but during human evolution, 2 fused together.

What evidence is there to support this?

Chromosome bonding patterns. The patters of human chromosome 2 is very similar to that of chromosome 12 & 13 in chimps

Is this strong evidence?

Yes - The bonding patterns and remnants of extra telomeres as well as the extra chromosome are strong evidence.

How can a hypothesis be scientifical?

If it is testable either experimentally or observably so the hypothesis can be proven false

Is the chromosome hypothesis scientifical?

Yes because evidence would be obtained to prove it false

What is a genome?

All the genetic information of one individual or a group of organisms. Its is the entire base sequence of the DNA molecule.

What functional units does a genome have?

Genes

What is a gene?

A length of DNA carrying hundreds/ thousands if bases.

Do members of the same species have the same genes?

Yes - they often have the same genes, in the same sequence, in each of their chromosomes

What does this do?

Promotes genetic diversity through meiosis

What does the genome of a species and the arrangement of genes on the chromosome illustrate?

the unity of living organisms

What are alternative forms of genes?

alleles - alleles of a gene differ from each other in the base sequence

What does SNPs stand for?

Single Nucleotide Polymorphins

What is a SNP

Positions in a gene where alternative bases may be found - 100 million have been discovered in humans

What does G - G mean between paternal and maternal alleles?

The child is homozyguos because the alleles inherited are the same

What does A- C mean between paternal and maternal alleles?

The child is heterozygous because the alleles inherited are different

What are the two types of variation in genomes?

1. Variation in genome size

2. Variation in base sequence

What is genome size?

The total amount of DNA in a species

There is a huge variation of genome sizes in….

Eukaryotes

Can gene numbers be changed in eukaryotic cells?

Yes - they can be added, removed, with sections of chromosomes duplicated or deleted.

Define a polyploidy?

The addition of whole sets of chromosomes

Genomes vary in the amount of ……….

non-coding DNA

What will differ in two populations of a species?

The position of their base sequence

What happens if the two populations diverge?

More differences will accumulate

After hundreds of millions of years, what will have happened?

Immense diversity will have developed in the base sequence.

How come in some gene base sequences there are few differences?

Because they are genes with a vital function e.g. cytochrome c-a protein used in respiration

What is genome size variations linked with

Organism complexity (not not always proportional with some unexpectedly large genomes)

How are genome sizes given in eukaryotes?

As nuclear DNA contents haploid cells like gametes

How are genome sizes given in prokaryotes?

As DNA content of a typical cell

What are the 2 types of measurement

1. In mass (pictograms e.g. 1pg = 10^-12 grams)

2. N° of base pairs/ megabase pairs (1 Mbp = 10^6 base pairs)

Define whole genome sequencing

Determining the entire base sequence of an organisms DNA.

The speed of sequencing is _________ and the cost is __________.

increasing rapidly, decreasing

What would happen if we sequenced the genomes of all species?

Would reveal relationships and evolutionary origins

What are the current uses of whole genome sequencing?

1. Allows an understanding of human origins and worldwide migration

2. Provides data about genetic diseases and genes affecting health

What are its future uses?

1. The possibility of sequencing every humans genome

2. Creating personalized medicine to predict and treat health problems

What happens if members if the same species interbreed by sexual reproduction?

Their traits are remixed generationally

Does the biological species concept work if a species interbreed BOTH sexually and asexually

Yes, so long as divergences between individuals is prevented

What do species reproducing asexually produce

Clones

What do mutations cause in clones

Causes them to split creating even more different species e.g. black berries

Define vertical gene transfer

Parents passing their genes to their offspring.

What is the evolution of life thought to be like?

A tree growing. When a new species forms, a new branch of the tree grows. The branch cant then rejoin (because different species in interbreed)

What organism does this not work for?

Bacteria

What transfer does bacteria have

Horizontal transfer

Define horizontal transfer

Genes sometimes transfer from one species to another, even if they are distantly related.

How does horizontal transfer work in bacteria?

How antibiotic resistant genes can move from one species to another.

What questions does this raise?

If the biological species concept works with prokaryotes.

What happens if 2 organisms with different chromosome numbers mate?

Their offspring would likely be unable to carry out meiosis (cant reproduce)

In terms of chromosomes, why would they not be able to reproduce?

Because some chromosomes would not be homologous to any other chromosome, so they would not be able to pair during metaphase 1. Then segregation of chromosomes into 2 haploid groups during anaphase 1 would fail

= No gametes produced

What is used to identify species that are not immediately recognised?

A dichotomous key :)

Explain how they work

1. They consist of a series of numbered stages

2. Each stage consists of a pair of alternative characteristics

3. Some will state where to go next, the others will name the species

Example of dichotomous key:

Define DNA barcode

A short section of DNA from a gene to identify a species

Define Environmental DNA

DNA obtained from soil, water, parts of abiotic environments. There are lots of organisms that interacted with the sample of environment.

What does DNA barcoding allow us to do with the environmental DNA?

It allows us to identify the biodiversity of habitats and investigate them. We can find what species have been where.