5.1.3 - Continuity of species

Question 1

Evaluate the impact of scientific knowledge on the manipulation of plant and animal reproduction in agriculture
- question break down

Answer 1

Evaluate: make a judgement (of the impact). Positivies and negatives

Scientific knowledge: identify and outline the techniques involved in the manipulation - e.g. techniques such as selective breeding, artifical insemination, cloning.

What effect does this have on the reproduction and continuity of species? How has this knowledge enables us to change plant and animal reproduction (timing, no./quality of offspring, genetic variability)

Must have plant and animal example (6 marks)

Question 2

Selective breeding

Answer 2

AKA artificial selection

• Development of particular phenotypic traits by choosing which males and females will reproduce to have offspring together.
• Aim is produce new and better combinations of traits by choosing parents who possess desired traits. These traits are passed on to offspring due to heredity
• Can take several generations for desired traits to become prominent in gene pool

Pros:
- Over time it gives rise to offspring who are genetically desirable to humans, e.g. cow with high muscle mass for beef

Cons:
- As only offspring with the most desirable traits are bred in each round, genetic diversity is decreased → lower resilience

E.g. labradoodles were bred by crossong labrador and poodle to produce a new variety with a different combination of characteristics (hybridisation)

E.g. thoroughbred racing horses, chihuahas

E.g. maize - 10,000 years ago Teosinte grass was domesticated in Mexico. It had small kernels enclosed by a hard fruit case and was highly branched, but over time as farmers continued pollinating only the plants with the most kernels and fewest branches, it was bred into corn.

Question 3

Artifical insemination

Answer 3

Semen is collected from an individual with desired phenotypic traits and used to fertilise a female.

Pros:
* It provides the desired quality → increases livestock productivity (e.g. milk/meat production)
* The offspring are guranteed to inherit desirable genes from their parents

Cons:
* Process requires well-trained operators + specialised equipment → costly
* Improper cleaning of instruments and in sanitary conditions may lead to lower fertility, spread of genital diseases
* Reduction of genetic diversity - can also propogate unhelpful genes.

E.g. Semen can be collected from a champion bull, frozen and sold across the world. The samples can be used to fertilise several females.

E.g. used on racehorses, dogs, and sheep

Question 4

Disadvantage of artificial breeding methods

Answer 4

All these methods reduce genetic diversity, decreasing biodiversity and the continuity of species.

Question 5

Artificial pollination

Answer 5

Oldest and simplest reproductive technique. Gregor Mendel!!!!!

The plants expresses desired traits (sweet fruit, colourful petals) - rubbing pollen on the stigma of another

Kiwis - they need 40 bee visits. So artificial pollination ensures that fruit produces. This is a positive

Question 6

Cloning - plant

Answer 6

Simplest form - asexual reproduction (cutting, grafting, runner)

Tissue culture
- Taking pieces of root tissues from a parent plant and culture them in a nutrient liquid in a lab.
- Calluses form from root cells and grow into a clone of the parent plant

Pros:
- Large scale cloning.

Question 7

Methods to alter plant and animal reproduction

Answer 7

• Selective breeding
• Artificial insemination
• Artificial pollination
• Cloning
• Tissue culture

Question 8

Natural selection vs selective breeding

Answer 8

Natural selections occurs in nature, but selective breeding only occurs when humans intervene.