5.2 - natural selection

Question 1

what is variation?

Answer 1

• each species has natural variation
• can be caused by sexual reproduction or mutation
• leads some individuals to be better suited to the environment
• for natural selection to happen there must be variation

Question 2

how is genetic variation caused?

Answer 2

through, mutation, meiosis, sexual reproduction

Question 3

what are mutations and how are they caused?

Answer 3

• mutations change the genetic composition of alleles, that changes the gene pool of a population
• gene mutaion changes the nucleotide sequence of a section of DNA that codes for a trait
• new alleles are formed by mutations

Question 4

what are the different types of mutations?

Answer 4

beneficial - missense
detrimental - nonsense
neutral - silent
*mutations are the only source of variation in asexually reproducing organisms

Question 5

how does meiosis cause mutations?

Answer 5

• during crossing over (prophase I) new combinations of alleles can be produced
• can also happen during independent assortment of genes (metaphase I)

Question 6

how does sexual reproduction cause variations and mutations?

Answer 6

• promotes variation as it involves random combinations between two gametes
• results in new gene combinations in offspring

Question 7

what are adaptions?

Answer 7

• characteristics of organisms that ensure they are better suited to their environment for survival
• different types - structural, behavioural, physiological, and biochemical.
• develop over time and species evolve over generations

Question 8

what are biological adaptions?

Answer 8

they are heritable traits and can be passed down to offspring by parents genes.

Question 9

what are the effects of overproduction of offspring?

Answer 9

• more offspring are born than can survive
• there is natural variability in offspring so some are more suited than others
• greater competition for resources, resulting in selection pressures
• only the most adapted can survive and reproduce to pass of genes
• change in gene pool and natural selection takes place.

Question 10

what is inherited by offspring?

Answer 10

• only heritable characteristics are passed on to offspring
• acquired characteristics are not passed down to offspring.

Question 11

what do progressive changes do?

Answer 11

the better-adapted individuals survive and can reproduce so it leads to an increase in the proportion of individuals with alleles that generate favourable characteristics.

Question 12

was was found on Daphne Major in the Galapagos Islands?

Answer 12

• out of 14 species of finch, 2 of them are on Daphne Major, medium ground finch and small ground finch
• longitudinal studies showed that their beak size was linked to their diet
• drought caused beaks to change because of food available.

Question 13

problems with antibiotics

Answer 13

• antibiotic resistance in pathogenic bacteria
• the resistance can be spread between species of bacteria by horizontal gene transfer
• this is an example of evolution that is from natural selection

Question 14

what are antibiotics?

Answer 14

• chemicals that can kill off and inhibit the growth of bacteria.
• antibiotics impose selection pressure on a population of bacteria.

Question 15

how do bacteria cells resist antibiotics?

Answer 15

• some bacteria cells may have a mutated gene with antibiotic resistance
• the cells with resistance have a selective advantage and can reproduce by binary fission to pass on these characteristics
• results in bacterial colonies that are resistant and the antibiotic wont be successful