12: Biodiversity Flashcards
Define Habitat & Community:
Habitat: place where an organism lives
Community: all the organisms in a habitat
What does Species Diversity consist of?
What is the Diversity Index formula?
- number of different species present
- number of individuals in each species
D = N(N-1) / sum of n(n-1)
N = Number of individuals of all species
n = number of individuals in a particular species
How can we avoid bias?
How can we get a representative sample?
- Random Sampling
- Use a very large number of quadrats (at least 20)
Describe Random Sampling:
- grid is laid out across the sample using tape measure
- random numbers are generated (i.e from random number generator) to provide coordinates for the grid
- these will be the sample points where frame quadrats are are placed
- within each quadrat, the number of species are counted + each organism in the quadrat is identified
- a very large number of randomly placed quadrats are required
Describe the Impact of Agriculture on Species Diversity:
- lower variety of habitats/niches (removal of grassland + hedgerows)
- fewer plant species, as only one crop is grown & weed removed/killed by herbicides
- few species of herbivores due to little variety of food
- lower types of carnivores, due to less herbivores
- lower diversity due to pesticides decreasing insect species
- low species diversity
How are Hedgerows a potential advantage for species diversity?
- provides habitats for organisms
- provides food + shelter for organisms
Define Gene:
Define Allele:
Define Genetic Diversity:
- short section of DNA that codes for a polypeptide
- different versions of a particular gene
- number of different alleles of genes in a population
What are the 3 causes of Genetic Variation?
What is the only way there can be variation in asexual organisms?
- mutation
- meiosis
- random fusion of gametes
Mutation
How can Gene Mutation lead to Non-Functioning Proteins?
- a gene is the sequence of bases in DNA that codes for the production of a protein
- if the sequence of DNA bases is altered in a gene, then this changes the sequence of bases in mRNA that is transcribed
- therefore this could change the sequence of amino acids translated for a protein
- this change in the primary structure of the protein causes a change in the tertiary structure, as hydrogen ionic and disulphide bonds form in different places
- this leads to a loss in function of protein
What is Meiosis 1?
What is Meiosis 2?
- homologous pairs separate, and the cells become haploid
- centromere breaks, and chromatids separate
How does Meiosis lead to Variation?
- it forms a new combination of alleles
- independent segregation of homologous chromosomes (meiosis 1)
- crossing over (meiosis 1)
Describe Independent Segregation (meiosis 1):
- at the start, homologous chromosomes pair up, and line up at the equator of the spindle
- this causes the orientation of the homologous chromosomes to be random
- these homologous chromosomes will then separate into, different combinations of maternal + paternal chromosomes in the gametes formed
How do you work out the number of combinations of maternal + paternal chromosomes?
2^n
where n = number of pairs
Describe Crossing Over (Meiosis 1):
- when homologous chromosomes associate, the form a bivalent and one of the chromatids of each homologous chromosome, get wrapped around each other at the chiasmata
- this can cause sections of each chromatid to break off an re-join to the chromatid of the homologous partner (this is crossing over)
- this is where alleles are exchanged between maternal + paternal chromosomes (genetic recombination)
- when the new chromosomes move apart, there will be a new combination of alleles
Describe the Differences between Meiosis + Mitosis:
- meiosis contains 2 divisions forming 4 daughter cells, mitosis contains 1 division forming 2 daughter cells
- mitosis has genetically identical offspring, whilst meiosis has genetically variant offspring
- meiosis contains (independent segregation + crossing over), mitosis does not
- meiosis produced haploid offspring, mitosis produces diploid offspring
