Changing Population Characteristics

Question 1

Selection pressures

Answer 1

• All organisms are exposed to selection pressures
• these are factors that affect the organisms chance of survival or reproductive success

Question 2

Natural selection steps :

Answer 2

1. Organisms within a species show variation in their characteristics that are caused by differences in their genes ( genetic variation )
   - They may have different alleles of a gene for a particular characteristic
   - new alleles can arise by mutation
2. Organisms whose characteristics are best adapted to a selection pressure such as prediction , completion or disease have an increased chance of surviving and successfully reproducing
   - less well adapted organisms die or fail to reproduce - survival of the fittest
3. Successful organisms pass the allele encoding the advantageous characteristic onto their offspring
   - conversely organisms that possess the non advantageous allele are less likely to successfully pass it on
4. This process is repeated for every generation
   - over time the proportion of individuals with advantageous adaptation increases
   - thus the frequency of the allele that codes for this particular characteristic increases the populations gene pool
5. Over very long periods of time many generations and often involving multiple genes this process can lead to the evolution of a new species

Question 3

Pesticides

Answer 3

Chemicals that kill pests of any kind including pests , pathogenic organisms or weeds

Question 4

Types of pesticides

Answer 4

Insecticides

Herbicides

Fungicides

Molluscicdes

Rodenticides

Question 5

Two ways bacterium inherit resistance to an antibiotic

Answer 5

• vertical transmission
• horizontal transmission

Question 6

Vertical transmission

Answer 6

• bacteria reproduce asexually by binary fission
• bacteria reproduce very rapidly every 20 mins
• if 1 bacterium contains a mutant gene that gives it antibiotic resistance all of its descendants will also have antibiotic resistance
• this form of transmission enables antibiotic resistance to spread within a bacterial population

Question 7

Horizontal transmission

Answer 7

• plasmids contain antibiotic resistant genes
• plasmids are frequently transferred between bacteria
• occurs during conjugation ( a thin tube forms between two bacteria to allow the exchange of DNA )
• in this way a bacterium containing mutant gene that gives it antibiotic resistance could pass this gene on to other bacteria
• this form of transmission enables antibiotic resistance to spread within or between bacterial populations

Question 8

Types of incorrect use of antibiotics

Answer 8

• for treatment of non serious infections
• routine treatment of animals in agriculture
• failure to finish the prescribed course of antibiotics

Question 9

Ways to Reduce cases of antibiotic resistance

Answer 9

• only prescribing antibiotics when necessary
• ensue patients complete courses of antibiotics
• rotate which antibiotics are used so that one type is not continually used in the treatment of a specific disease