Unit 3 Flashcards
Definition of food security
the ability of a human population to access food of sufficient quality and quantity
Natural factors which affect food production (5)
drought, pests, flooding, disease, desertification
Damage to environment which must be avoided during food production (5)
global warming, pollution, deforestation, soil erosion, reducing soil fertility
Limiting factors of plant growth (6)
Light intensity, CO2 concentration, temperature, availability to nutrients, pests and diseases, competition
Intensive farming practices and their effects (3)
Growth of higher yield crops - higher yield cultivar is created or selected and maintained through cultivation
Fertilisers - give increases crop yield
Pesticides - crops are protected from pests, diseases and competition through insecticides, herbicides and fungicides
How is energy lost in a food chain?
Heat, waste and movement
What happens to the light that hits a leaf?
83% is absorbed, 12% is reflected and 5% is transmitted
What do the black bars on an absorption spectrum represent?
light wavelengths that are absorbed
What does an absorption spectrum show?
the wavelengths of light absorbed by different pigments in a leaf
What does an action spectrum show?
the rate of photosynthesis at different wavelengths of light
What is the function of accessory pigments?
to extend the range of wavelengths that can be absorbed
What is the first stage of photosynthesis called?
The light dependent stage
What does light energy do to electrons?
excites them and raises them to a higher energy state
What enzyme turns adp into atp?
ATP synthase
What is energy used for in the first stage of photosynthesis?
to phosphorylate ADP (make ATP)
photolysis of water (splitting of water into hydrogen and oxygen)
What does hydrogen bind to and make in the first stage of photosynthesis?
hydrogen binds to NADP to form NADPH
What is a by-product in stage 1 of photosynthesis?
oxygen
What is the second stage of photosynthesis called?
Carbon fixation or the calvin cycle
What is used in stage 2 of photosynthesis from stage 1?
ATP and NADPH
What does RuBisCO do in stage 2 of photosynthesis?
attach carbon dioxide to RuBP
What forms when carbon dioxide attaches to RuBP in stage 2 of photosynthesis?
3PG
What is 3PG used for?
it is phosphorylated by ATP and joins the hydrogen from NADPH to from G3P
How is G3P formed?
3GP joins with hydrogen from NADPH
What is G3P used for?
to regenerate RuBP and to synthesise glucose
What does the glucose produced in stage 2 of photosynthesis do?
some is converted into starch
some is used to produce energy in respiration
some is converted into cellulose for cell walls
Reasons to alter an organisms genetics (5)
higher yield, increase in nutritional value, resistance to disease/pests, to survive particular environmental conditions, to make it more suitable for harvesting
What is a cultivar?
a plant that has been created or selected intentionally for desirable characteristics which can be maintained through cultivation
What is a plant field trial?
an experimental investigation in an organisms natural environment instead of a lab
What can plant field trails evaluate? (3)
the performance of different cultivars in a range of environments
the effects of different treatments such as pesticides or fertilisers
genetically modified crops
Required when designing plant field trials
careful selection of treatments/variables
replicates (several trial plots increases reliability)
randomisation (where treated and controlled areas are across the plot)
What is inbreeding?
closely related plants and animals are bred for several generations until they breed true to the desired type due to the elimination of heterozygotes
What is inbreeding depression?
an accumulation of homozygous recessive alleles which can be deleterious
can result in loss of vigour, poor general health, reduced size, reduced fertility, reduced yield
What can inbreeding lead to? (2)
loss of heterozygosity
inbreeding depression
How are F1 hybrids produced?
the crossing of 2 different inbred homozygous cultivars
Why are the F2 generation not favourable?
can be too genetically diverse
can lack the improved characteristics seen in the F1
2 forms of genetic technology
genetic sequencing
genetic transformation
What is genome sequencing used for?
can be used to identify organisms that possess particular alleles for a desired characteristic
2 types of weeds
perennial
annual
Properties of perennial weeds (3)
grow for several seasons
sexual and asexual reproduction (vegetative)
storage organs