Biodiversity Flashcards
what is genetic diversity?
Genetic diversity is the number of different alleles within a population.
What is a population?
A population is a group of the same species, in the same place that can interbreed
What is the result of genetic diversity?
-More Genetic Diversity = More Alleles
-Wider Range of Characteristics/Variation (bigger gene pool)
-Greater Chance of Individuals Surviving
Environmental Change
Use the example of the giraffes with long necks in to explain how a change in the environment leads to the length of necks increasing
-Change in environment causes a selection pressure.
-Random mutations produce genetic diversity- alleles for neck.
-Some alleles provide an advantage to gaining resources.
-Those individuals with the alleles survive and reproduce.
-Advantageous alleles are passed on.
-The frequency of advantageous alleles in the population increases.
-Frequency of long neck increases.
Who decides what is advantageous?
either the environment or nature
What is the mnemonic to remember?
Some - selection pressure
Really - random
Mental - mutations
Goats - genetic diversity
Ate - advantage
Some - survive
Raw - reproduce
Premium - pass on alleles
Fish - freq of alleles increase
Fingers - frequency of trait increase
Explain variation BETWEEN species
Different species have different genes.
They may also have a different number of chromosomes.
They cannot breed to produce fertile offspring and have different features.
Explain variation WITHIN a species
All members of the same species have the same genes.
Members of the same species differ due to their allele combinations.
What is selection?
The process by which organisms that are better adapted to their environment survive and reproduce, while those who are less well adapted do not.
What is a selection pressure?
An environmental change that leads to selection.
What are the types of variation?
continuous and discontinuous
What is continuous variation?
A characteristic that can have a wide range of values shows continuous variation.
Producing a histogram of continuous variation produces what kind of distribution curve?
A ‘bell shaped’ normal distribution curve
What is discontinuous variation?
A characteristic with few possible values shows discontinuous variation. There is no bell curve
What are most characteristics controlled by?
Most characteristics are controlled by multiple genes/alleles (polygenic) so show more variation.
What is the difference between polygenic traits and monogenic traits?
Polygenic traits are more influenced by the environment than monogenic traits. The environment affects gene expression - more genes more exposure to environment.
What 2 effects can selection produce on a population?
-Favouring individuals that vary from the mean -directional selection.
-Favouring the average individuals - stabilising selection.
What is directional selection?
Favouring individuals whose characteristics vary from the mean.
Phenotypes are selected for. Genotypes are indirectly selected.
What are some things we should remember about mutations?
-Mutations do not occur because of selection pressures
-Mutations are random and rare
-Most do nothing or are harmful and lead to death.
-A mutation leading to an advantage is a result of chance
-Bacterial populations are large so chance is greater
How can the rate of mutations increase?
-due to environment
What is stabilising selection?
-If conditions remain stable, individuals with average characteristics are favoured.
-Phenotypes at the extremes are selected against. Genotypes are indirectly being selected.
What does increased proportion =?
increased proportion=well adapted
What do directional and stabilising selection do to characteristics?
Directional selection CHANGES
CHARACTERISTICS, Stabilising selection
PRESERVES CHARACTERISTICS.
What do courtship behaviours allow individuals to do?
-Recognise of members of the same species.
-Identify a sexually mature mate.
-Form a pair bond that will lead to successful mating and raising of offspring.
-Synchronise mating so that it takes place at a time where egg and sperm are most likely to meet.
-Become able to breed by bringing a member of the opposite sex into a state that allows breeding to occur.
Classifying species allows for what?
-Better communication
-Avoiding confusion
What is artificial classification?
Grouping organisms based on features that are useful at the time e.g. colour, wings. The evolutionary origin of these features are different.
What is phylogenic classification?
-Based on evolutionary relationships or phylogeny (evidence from fossils, DNA analysis)
-Based on shared ‘homologous’ features, derived from their evolutionary ancestors.
-Arranges organisms into groups called hierarchies in which are split into composite (smaller) groups which do not overlap.
What type of characteristics is phylogenic classification partly based on?
homologous characteristics
What are homologous characteristics?
Homologous characteristics have similar evolutionary origins regardless of their function.
e.g. wing of a bird, arm of a human, front leg of a horse
All have the SAME basic structure and evolutionary origins and are therefore homologous.
What is the scientific name for groups?
‘Taxon’ pl. ‘Taxa’
What is the study of groups?
taxonomy
What are the difference taxonomic ranks that we need to know?
Domain (Divine)
Kingdom (Kings)
Phylum (Play)
Class (Chess)
Order (On)
Family (Fat)
Genus (Green)
Species (Stools)
What did Aristotle do?
Aristole was 1st taxonomist and he classified organisms into either plants or animals, then he sub-divided based on their habitat - land, water, air
What did John Ray do?
John Ray was next he was the first to use a Latin name however, his names were VERY long describing everything and anything about the organism
What did Carl Linneaus do?
Carolus Linneaus (18th century) - he classified based on structure and developed a common naming system still in use today - binominal system (two words ‘genus’ ’specie’)
What is the binomial system?
-In this system an organisms is given a name consisting of 2 words
-Its universal based on Latin and Greek names
-1st name is generic name ‘ genus’ - this is like the surname
-the 2nd name is specific name ‘specie’ - this is like the forename (unlike in humans this is NEVER shared by any other species within the genus)
-Genus always has a capital letter, specie is lower case
What are the benefits of classifying?
-Makes everyone stick to the same name!
Uses the same language for all organisms (Latin or Greek)
-If used different languages to name organisms we would end up with one organism having
-MANY different names - this method avoids this and so only ONE name is universal
-Latin/ Greek names are understood by taxonomists
What is species diversity?
the number of different species in a community and their proportions
What is ecosystem diversity?
the number of different habitats that make up an ecosystem
What is meant by species richness?
The number of different species in a community
What is the species richness for habitats X and Y?
5
Why is species richness not very helpful for comparing the species diversity in these 2 habitats?
Because it only tells you the number of species in an area and not the proportions of individuals that make up each species.
Why is it better to measure species diversity by calculating an index of diversity?
Because it takes into account the proportion of individuals in each species as well as the number of species. It is a quantitative measurement rather than qualitative.
What is the equation for calculating the index of diversity?
Why is it better to measure species diversity by calculating an index of diversity?
Because it takes into account the proportion of individuals in each species as well as the number of species. It is a quantitative measurement rather than qualitative.
How do human activities have an impact on the world?
The UK population has risen from just over 50 million in 1960 to 65 million today.
In our efforts to provide enough food at low cost we have had a significant impact on the natural world.
What is an ecosystem?
An ecosystem consists of a community of organisms and the habitats in which they live.
What is a natural ecosystem?
Natural ecosystems develop overtime and form complex communities with huge biodiversity.
What are artificial ecosystems?
Agricultural ecosystems are artificial - controlled by humans.
Farmers select which species are allowed to grow there.
They have a low genetic diversity, species richness and index of diversity.
What do plant compete for?
minerals, water, light and space
Why do farmers remove competition?
Farmers remove competition so that land is occupied by desired species.
When farmers remove competition, what is the impact on biodiversity?
By reducing competition, few species dominate.
Genetic diversity decreases.
Species richness decreases.
Index of diversity decreases.
so
Fewer Habitats
Variety of plants/insects/animals decrease.
Variety of food decreases.
How can we develop evolutionary relationships?
Observe physical characteristics
Observe proteins/enzymes.
Observe amino acid sequence.
Observe mRNA sequences.
Observe DNA sequences
Traditionally, what was genetic diversity measured with?
-observable characteristics
this is because genes code for characteristics
What are the problems with observable characteristics?
-Some characteristics are polygenic (may be more alleles than thought).
-The environment may be influencing a characteristic (may be less alleles than thought)
How can we measure genetic diversity now?
We can now read the DNA sequence of any organism.
We can determine the exact order of nucleotide bases.
This is now automated using machines.
Each base is tagged with a colour: adenine, guanine, thymine, cytosine.
This produces a ‘heat map’ which can be easily compared
How does phylogenetic classification occur?
After speciation occurs, the DNA sequences of new species are similar. They accumulate random mutations over time.
As a result, more closely related species show more DNA similarities. This is allows for phylogenetic classification.
How is it possible to compare genetic diversity by comparing mRNA?
mRNA is coded for by DNA.
mRNA is complementary to the DNA from which it is transcribed.
Therefore, if we can compare genetic diversity using DNA, we can also compare it by looking at mRNA.
How is it possible to compare genetic diversity by comparing amino acid sequence?
Amino acid sequence is determined by mRNA
sequence, which is determined by DNA sequence.
Therefore, this can be used to compare genetic diversity within and between species.
More closely related species will have more similarities in amino acid sequences.
What are the different types of variation?
interspecific
intraspecific
What is interspecific?
variation in characteristics between species.
What is intraspecific?
variation in characteristics between members of the same species.
What is sampling?
This is where scientists look at smaller group of organisms.
In theory, they should be representative of the whole population.
This is not always the case due to sampling bias
What is sampling bias?
Scientists may show bias in the way they are collecting samples.
E.g. avoiding wet mud and nettles when counting buttercups.
How can we eliminate sampling bias?
Draw a grid over a map of the land.
Use a random number generator to generate coordinates.
Place quadrat at coordinates.
How does chance correlate with sampling?
Even without bias the measured value may be down to chance.
E.g. 50 chosen buttercups may all happen to be tall ones!
How can the impact of chance be reduced?
-Increase sample size e.g. more or bigger quadrats.
You are less likely to
choose 500 tall buttercups than 50 tall buttercups.
-Carry out a statistical test
this tells you exactly how confident you can be that the result is not due to chance. We usually aim to be 95% confident.
How would continuous variation be
displayed on a graph?
If you measured a characteristic of a population that showed continuous variation under stable conditions it would present a normal distribution.
What are the features of displayed continuous variation?
Symmetrical.
Mean, median and mode values are the same.
Sometimes skewed
Why might a distribution curve appear skewed sometimes ?
Insufficient sampling - overrepresentation of anomalies.
An external factor/selection pressure favouring a characteristic.
Normal distribution curves differ in which two aspects?
height and width
What does the height of a distribution curve tell us?
the mean
What does the width of the distribution curve tell us?
the range of values
less width=?
less variation
The average distance of each point from the mean is called the..?
standard deviation
What is the equation to calculate SD?
How do you calculate SD?
