Manipulation of the food species
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Advantages of high population of both crops and animals
• increased yield • pest control • better soil health • efficient land use
Disadvantages of high population of both crops and animals
• increased competition • disease spread • soil degradation
Advantages of low population of both crops and animals
• reduced competition • lower disease risk • improved soil health • enhanced biodiversity
Disadvantages of low population of both crops and animals
• lower yield • vulnerability to pests • limited genetic diversity
Optimum population density changes for each farm/area and is dependent on:
• crop type • soil quality • water availability • climate
Definition of a monoculture
1 species covering a fairly large area low genetic diversity
Advantages of monoculture
• efficient harvesting • minimal technology • higher yield • higher income
Disadvantages of monoculture
• low genetic diversity • increased disease • low biodiversity - less stable
Selective breeding description
Agents are selected with desired traits Offspring then express these desired characteristics Frequency increases over generations
How have chickens been selectively bred for food consumption
Faster egg production - kept in battery cages, breed the hens which lay the most eggs Faster meat production - kept intensively in large sheds, chose chickens with higher meat mass
How have cows been selectively bred
For meat - ancestor had mutation ‘double muscling’ Disadvantages - causes difficulties when the cows give birth
Example of selectively bred plant
Wild Mustard Plant - leaves used for kale and flower buds used for cauliflower
Define crossbreeding
2 different varieties of the same species - genetically different
What are the general characteristics of a crossbred hybrid breed
Traits of both parents - e.g. labradoodle High genetic diversity Bigger and stronger
Example of a crossbred plant
Different varieties of a tomato Characteristics: disease-resistant and high yield
Example of a crossbred animal
Zebu (does well in hot climates) + Ayrshire (high milk yield) Offspring - high milk yield, heat tolerant
What is artificial insemination
Process of injecting a male semen into a females cervix when she is in oestrus
Benefits of artificial insemination
Useful for breeds at risk Ensures survival of rare gene pools Diseases are less likely to spread - as women don’t have to be transported to the stud
Describe the process of embryo transfer
Females + hormone FSH Produce many eggs Eggs collected and fertilised with desired sperm Fertilised embryos implanted into surrogates
Define asexual reproduction
Only using one parent for producing offspring identical to the parent
Advantages if asexual reproduction
Occurs quickly No need for mates Lower risk of disease
Disadvantages of asexual reproduction
No introduction of new genetics Vulnerable to environmental change Overpopulation
2 methods of artificial vegetative propagation
Cutting Micropropagation
What is cutting
Take a cutting and add a rooting hormone Then plant the cutting And it will grow roots