Unit 3 biology

What is food security

Ability of human populations to access suffcient quantity and quality of food

What does an increase in human population result in

a concern for food security → demand for increased food production

what must food production be

sustainable and not degrade natural resources in which agriculture depends on

what is all food production ultimately dependant on

Photosynthesis

Agriculture production depends on factors that control

photosynthesis and plant growth

what are these factors that control photosynthesis and plant growth

nutrient availability, water availability, light , temperature, carbon dioxide availability

livestock produce…

less food per unit area than crop plants due to energy loss of energy between trophic levels

live stock production is often possible in

habitats unsuitable for growing crops

Breeders seek to develop crops with

Higher nutritional values,

resistance to pests and diseases,

Physical characteristics suited to rearing and harvesting as well as those that can thrive in particular environmental conditions

How is light energy absorbed and what is it used for

by photosynthetic pigments to generate ATP and for Photolysis

Light energy is _______ and _____ but not _______

transmitted or reflected but not absorbed

chlorophyll a and b absorb

blue and red wavelengths of the spectrum

carotenoids

extend the range of wavelengths absorbed and pass the energy to chlorophyll for photosynthesis

each pigment absorbs a

different range of wavelengths of light

light dependant stage

Electrons get Excited
Electrons pass through electron transport chain

ATP generated by ATP synthase

Energy used for photolysis

Energy used to split water to produce hydrogen and oxygen

Oxygen is evolved/released

Hydrogen ions joins to coenzyme NADP producing NADPH

ATP and NADP are transferred to the Calvin Cycle

Carbon Fixation

the enzyme RuBisCO fixes carbon dioxide

by attaching it to RuBP

3PG produced is phosphorylated by ATP and

combined with hydrogen ions from

NADPH G3P

G3P is used to regenerate RuBP and for the synthesis of glucose

what is glucose used for

as a respiratory substrate, synthesised into starch or cellulose or passed to other biosynthetic pathways.

what can biosynthetic pathways lead to the formation of

variety of metabolites such as:

DNA,

protein

fat

Breeders develop crops and animals with

higher food yields, ,

higher nutritional values,

pest and disease resistance

ability to thrive in particular environmental conditions.

Plant field trials are carried out in a

range of environments to compare the performance of different cultivars or treatments and to evaluate GM crops.

In designing field trials account has to be taken of the

selection of treatments

the number of replicates

the randomisation of treatments.

The selection of treatments to ensure

valid comparisons

the number of replicates

to take account of the variability within the sample

the randomisation of treatments to

eliminate bias when measuring treatment effects.

Inbreeding

Relatives are bred for several generations

This eliminates heterozygosity

which increasins homozygosity

Inbreeding depression occurs

Inbreeding depression is an accumlation of deleterious homozygous, recessive alleles

Inbreeding depression reduces fertility which leads to poor reproductive rates

Crosssbreeding

crossbreeding is breeding different cultivars

which results in f1 hybrids

offspring have desirable alleles

so new alleles introduced

Crossbreeding produces a uniform heterozygous f1

f1 has increased vigour/disease resistance/growth rate/yeild

f1 are not usually not bred together as f2 are too varied

parents breeds maintained to produce more crossbreeds

Single genes for desirable characteristics can be

inserted into the genomes of crop plants, creating genetically modified plants with improved characteristics.

Breeding programmes can involve crop plants that have been genetically modified using

recombinant DNA technology.

Weeds compete with

crop plants, while other pests and diseases damage crop plants, all of which reduce productivity.

Properties of annual weeds

rapid growth,

short life cycle,

high seed output and

long-term seed viability

Properties of perennial weeds with competitive adaptations

storage organs and vegetative reproduction.

Most of the pests of crop plants are invertebrate animals such as

insects, nematode worms and molluscs.

Plant diseases can be caused by

fungi, bacteria or viruses, which are often carried by invertebrates.

Control of weeds, other pests and diseases by CULTURAL METHODS

Ploughing, weeding and crop rotation

Pesticides include

herbicides to kill weeds, fungicides to control fungal diseases, insecticides to kill insect pests, molluscicides to kill mollusc pests and nematicides to kill nematode pests

Selective herbicides have a

greater effect on certain plant species (broad leaved weeds).

Systemic herbicide spreads

through vascular system of plant and prevents regrowth.

Systemic insecticides, molluscicides and nematicides spread

through the vascular system of plants and kill pests feeding on plants.

Applications of fungicide based on disease forecasts are more effective

than treating diseased crop

Bioaccumulation and Biomagnification

a build-up of a chemical in an organism. Biomagnification is an increase in the concentration of a chemical moving between trophic levels

In biological control the control agent is a

natural predator, parasite or pathogen of the pest.

Integrated pest management is a

combination of chemical, biological and cultural control

Risks with biological control.

The control organism may become an invasive species, parasitise, prey on or be a pathogen of other species

Intensive farming is less ethical than free range farming due to

poorer animal welfare

Free range

requires more land and is more labour intensive but can be sold at a higher price and animals have a better quality of life

Intensive farming

often creates conditions of poor animal welfare but is often more cost effective, generating higher profit as costs are low.

Behavioural indicators of poor animal welfare are

stereotypy, misdirected behaviour, failure in sexual or parental behaviour and altered levels of activity which are Very low apathy or very high hysteria

what is symbiosis

co-evolved intimate relationships between members of two different species

two types of symbiotic relationship

parasitism and mutualism

whats a parasite

benefits in terms of energy or nutrients, whereas its host is harmed by the loss of these resources

Parasites often have limited

metabolism and cannot survive out of contact with a host.

3 ways parasites transfer to new hosts

direct contact

resistant stages

vectors

Some parasitic life cycles involve

intermediate (secondary) hosts to allow them to complete their life cycle.

what is mutualism

when Both mutualistic partner species benefit in an interdependent relationship

Many animals live in social groups and have behaviours that are adapted to group living such as

social hierarchy, cooperative hunting and social defence

what is social hierarchy

its a rank order within a group of animals consisting of a dominant and subordinate members. In a social hierarchy, dominant individuals carry out ritualistic (threat) displays whilst subordinate animals carry out appeasement behaviour to reduce conflict.

Social hierarchies increase the chances of

the dominant animal’s favourable genes being passed on to offspring. Animals often form alliances in social hierarchies to increase their social status within the group

Co-operative hunting may benefit

subordinate animals as well as dominant ones, as they may gain more food than by foraging alone. Less energy is used per individual. Co-operative hunting enables larger prey to be caught and increases the chance of success.

Social defence strategies increase the chance of

survival as some individuals can watch for predators whilst others can forage for food. Groups adopt specialised formations when under attack protecting their young.

Altruism

An altruistic behaviour harms the donor individual but benefits the recipient.

Reciprocal Altruism

where the roles of donor and recipient later reverse, often occurs in social animals.

Behaviour that appears to be altruistic can be common between

a donor and a recipient if they are related (kin).

The donor will benefit in

kin selection in terms of the increased chances of survival of shared genes in the recipient’s offspring or future offspring

Social insects include

bees, wasps, ants and termites.

Most members of the colony are

sterile workers who co-operate with close relatives to raise relatives.
WHILE
only some individuals (queens and drones) contribute reproductively

Other examples of workers’ roles include

defending the hive, collecting pollen and carrying out waggle dances to show the direction of food

Sterile workers raise

relatives to increase survival of shared genes

Primates have a long period of

parental care to allow learning of complex social behaviour

Complex social behaviours support

the social hierarchy. This reduces conflict through ritualistic display and appeasement behaviour
Grooming, facial expression, body posture and sexual presentation.

Alliances form between individuals, which are often used to

increase social status within the group

components of biodiversity

are genetic diversity, species diversity and ecosystem diversity.

Genetic diversity

is the number and frequency of all the alleles within a population

If one population of a species dies out then the species may have

lost some of its genetic diversity, and this may limit its ability to adapt to changing conditions

Species diversity

comprises the number of different species in an ecosystem (the species richness) and the proportion of each species in the ecosystem (the relative abundance).

A community with a dominant species has a

a lower species diversity than one with the same species richness but no particularly dominant species.

Ecosystem diversity refers to the

number of distinct ecosystems within a defined area.

overexploitation

populations can be reduced to a low level but may still recover. Some species have a naturally low genetic diversity in their population and yet remain viable.

The bottleneck effect

small populations may lose the genetic variation necessary to enable evolutionary responses to environmental change

In small populations, this loss of genetic diversity can be critical for many species, as inbreeding can result in poor reproductive rates

what leads to habitat fragmentation

The clearing of habitats

Degradation of the edges of habitat fragments results in

increased competition between species as the fragment becomes smaller. This may result in a decrease in biodiversity

what can be done to remedy widespread habitat fragmentation

isolated fragments can be linked with habitat corridors.

The corridors allow

movement of animals between fragments, increasing access to food and choice of mate. This may lead to recolonisation of small fragments after local extinctions

Introduced (non-native) species are those that

humans have moved either intentionally or accidentally to new geographic locations.

naturalised species

Those that become established within wild communities

Invasive species

are naturalised species that spread rapidly and eliminate native species, therefore reducing species diversity. Invasive species may well be free of the predators, parasites, pathogens and competitors that limit their population in their native habitat. Invasive species may prey on native species, outcompete them for resources or hybridise with them