Selection And Variation

Question 1

What are the causes of genetic variation

Answer 1

▪️crossing over between inner non sister chromatids of homologous chrs forming new combination of alleles during meiosis prophase 1
▪️independent assortment of chrms as homologous chrs forming a double line at the equator independent on one another during metaphase 1
▪️random mating between organisms within a species
▪️random fertalisation of gametes
▪️mutations

Question 2

When do mutations happen

Answer 2

During DNA replication

Question 3

What is the difference between discontinuous variation and continuous variation

Answer 3

Disc
Qualitative
Different alleles occupying same Locus on homologous chromosomes have large effects on the phenotype
Different genes have different effects on the phenotype

Con
Quantitative differences in phenotype with many intermediate between the two extreme phenotypes
Different alleles of the same gene have small effects on the phenotype
Polygenes

Question 4

Describe the process of evolution by natural selection

Answer 4

Genetic variation fur to random mutations and selection pressures
Best adapted survive inc their advantaged allele
Less adapted die
Best adapted reproduce inc their allele freq in the gene pool
Evolution occurs over several generations

Question 5

What is stabilizing selection

Answer 5

Environmental selection pressures are acting on 2 extreme phenotypes of population
So all population line in the middle

Question 6

What is directional selection

Answer 6

If selection pressure acts only against one extreme phenotype due to environment changes it leads to directional selection favoring one allele over the other

Question 7

What is disruptive selection

Answer 7

When selection pressure is against middle phenotype splitting the population in to 2

Question 8

What are the consequences of inbreeding

Answer 8

Inbreeding depression
Non favorable appear(mention) due to increased homozoygozity
Increased chances of harmful recessive alleles to appear
Decreases the gene pool due to loss of alleles

Question 9

Explain hybridization and its effects

Answer 9

Crossing over species with different genotypes or close related ones
Leads to:
Outbreeding enhancement 
Hybrid vigor(good features)
Inc heterozygozity 
Better adaptations to changing env
Maintains gene pool

Question 10

Define the term species

Answer 10

Organisms with the same morphological,physiological,biochemical,and behavioral features and can interbreed producing fertile offsprings
And reproductively isolated from other species

Question 11

What are the types of reproductive isolation

Answer 11

Pre zygotic and post zygotic

Question 12

Allopatric speciation

Answer 12

Due to geographic barrier
Stops gene flow
Diff env conditions in each area so diff selection prs
Diff alleles are being selected for
Change allele freq in area
Natural random mutations introduce new alleles in gene pool causing genetic drift

Question 13

Sympatric speciation

Answer 13

Genetic barrier
Reproductively isolated(define pre or post zygotic)
Which results in natural mutation and formations of polyploids
Due to chromosomal non disjunction
Gametes form by mitosis
Doubling number of chrs along generations
Polyploids have more than 2 sets of chrms
Triploids result from fusion of a haploid and diploid gametes and are infertile due to odd set of chrs
Bivalents cant form
Tetraploids from fusion of 2 diploid gametes and have 4 sets of chrs and are fertile
Allotetraploids are more fertile than autotetraploids as they form bivalents

Question 14

Spearmen’s correlation

Answer 14

To find out if there is a correlation between 2 sets of data when its not normally distributed(discontinuous)
The closer the value to 1 the more likely there is a correlation between 2 sets of data

Question 15

Pearson’s linear correlation

Answer 15

Used when data collected is continuous and show normal distribution

Question 16

When is random sampling used

Answer 16

When area looks uniform and there is no clear pattern to the way the species are distributed