Diversity, Classification and Variation-Topic 4B Flashcards
What does Meiosis involve?
DNA from one generation is passed on to the next by gametes
What is a zygote?
When a sperm and egg cell (gametes) join together at fertilisation.
Normal body cells have the diploid number (2n) of chromosomes. What does this mean?
Each cell contains two of each chromosome, one from the mum and one from the dad.
Gametes have a …… (…) number of chromosomes
Gametes have a haploid (n) number of cells.
half number of chromosomes as diploid cells
How is genetic diversity increased within a species?
Fertilisation is random which produces zygotes with different combinations of chromosomes to both parents. (mixing of genetic material)
Gametes are formed by…..
Meiosis
Where does Meiosis take place?
In the reproductive organs
Cells that divide by meiosis are ….. to start with, but the cells that are FORMED from meiosis are …..
Cells that divide by meiosis are diploid to start with but the cells that are formed from meiosis are haploid.
What is crossing over?
Homologous pairs of chromosomes pair up and chromatids twist around each other and swap over. They contain the same genes but now different combinations of alleles.
Meiosis produces cells that are……..
Meiosis produces cells that are genetically different
Name the 2 main events during meiosis that lead to genetic variation
Crossing over of chromatids
Independent segregation of chromosomes
What does the crossing over of chromatids in meiosis I mean for the 4 daughter cells.
They contain chromatids with different alleles.
What are chromosome mutations caused by?
errors in cell division
In humans, if meiosis works properly all four daughter cells should end up with …. ………..
23 chromosomes
What is non-disjunction?
a failure of chromosomes to separate properly e.g. non-disjunction of chromosome 21 can lead to Down’s Syndrome.
What is Down’s Syndrome caused by?
A person having an extra copy of chromosome 21. Usually one cell gets an extra copy of 21 and another gets none. This means 3 copies of chromosome 21 due to extra copy fusing with another gamete.
What do gene mutations involve?
A change in the DNA base sequence of chromosomes
Give two examples of gene mutations
Deletion and substitution.
How are gametes produced?
Meiosis
What is independent segregation?
separating chromosomes into random combinations
What is genetic diversity
The number of different alleles of genes in a population.
Two organisms belong to the same species if…
they are able to produce fertile offspring
How is genetic diversity increased within a population?
Mutations forming new alleles
Different alleles introduced into population
Genetic Diversity allows what to occur?
Natural selection
Outline how Natural selection increases advantageous alleles in a population
Random mutation = new alleles of gene
Some mutations produce beneficial alleles leading to more reproductive success
Advantageous allele inherited by next generation
Increasing frequency of advantageous allele in the population
What type of selection does antibiotic resistance show?
Directional Selection
What is Directional Selection?
Where individuals with alleles for characteristics with an extreme type are more likely to survive and reproduce. This could be in response to an environmental change.
What is Stabilising Selection?
Where individuals with alleles for characteristics towards the middle range are more likely to survive and reproduce. Occurs when environment ISN’T changing
Name some aseptic techniques that should be used when investigating effect of antibiotics on bacterial growth
Disinfect work surfaces, and utensils shouldn’t be left on surface.
Use sterile equipment and discard safely after use
Work near Bunsen flame to draw microbes way from culture
Minimise time spent with lid off to reduce airborne microorganisms contaminating the culture.
Why are aseptic techniques used?
To prevent contamination as it can affect growth of microorganism or could contaminate with disease causing organisms and get ill.
Give the Index of Diversity equation and explain what each part represents
𝐷 = 𝑁(𝑁-1) / Ʃ 𝑛(𝑛-1)
N= total number of organisms of all species
n=total number of organisms of one species
Ʃ = sum of (added together)
What does the number calculated by the Index of Diversity mean?
The larger the number the more diverse the area is.
If there is no biodiversity the number Is 1
What agricultural practices can reduce biodiversity?
Pesticides, Herbicides, Monoculture (only 1 type of crop which will therefore support fewer organisms)
hedgerow removal- reduces hedges and no. of different types, destroying habitats and killing species or forcing to migrate.
Woodland clearance= same as hedgerow but with trees
Define Biodiversity
Variety of living organisms in an area
Define Habitat
Place where an organisms lives
What is a community?
All the populations of different species in a habitat
How can you know that two organisms belong to the same species?
Two organisms belong to the same species if they are able to produce fertile offspring
Courtship behaviour is used to…
attract a mate of the right species
Courtship is …… specific
species specific- only members of same species respond to that courtship behaviour, preventing interbreeding and making reproduction more successful. (species recognition.) This specificity allows courtship behaviour to classify organisms.
How does a Phylogenetic classification system arrange species?
Based on their evolutionary origins and relationships. Each group called a taxon (plural taxa) (more closely related down the groups)
Homo sapiens. Which is the genus and which is the species?
Homo = genus (capital letter) sapiens = species
What advances help to clarify evolutionary relationships between organisms?
immunology and genome sequencing.
Genetic diversity within or between species can be made by comparing…
the frequency of measurable or observable characteristics
the base sequence of DNA
the base sequence of mRNA
the amino acid sequence of the proteins encoded by DNA
(if share similar aa seq = more closely related)
Investigating variation you must make sure results are ….. to do this ….
Random
e.g. divide field into grid and use random number generator
AND carry out statistical test to make sure sample not due to chance.
What does a large standard deviation mean?
That the values in the sample vary a lot.
What does a small standard deviation tell you?
That most the sample data = around mean value so varies very little
Suggest how a student would obtain data to give a more precise value for the index of diversity of this habitat [2]
- Random sampling e.g. random number generator to know coordinates to place quadrats along grid
- Take MORE samples and find a mean
fewer species of plant in the oil palm plantation. Lizards feed on plants and insects. Explain why fewer species of plant would lead to fewer species of lizard in the oil palm plantation. [3]
Fewer species of plants =
fewer habitats
therefore fewer insect species/lower diversity
fewer food sources
What is species richness?
Number of different species in a community
What are some assumptions made with the mark release re-capture method? [2]
Marking doesn’t affect survival
No immigration
(or birth and death rate are equal)
What two measurements are needed to calculate an index of diversity? [2]
The total number of individuals of each species
The total number of species
Scientists analysed the samples of DNA to find genetic diversity
In this investigation, what is meant by genetic diversity? [1]
number of different base sequences found in each gene
