Paper 2 Flashcards
Homeostasis and Response, Inheritance, Variation and Evolution, Ecology
1
Q
What is the function of the cerebral cortex
A
consciousness, intelligence, memory, language
2
Q
What is the function of the cerebellum
A
coordinates muscle activity
3
Q
What is the function of the medulla
A
unconscious activity
4
Q
How does an electrical impulse pass between two neurones
A
- synapse
- chemical released into the gap
- chemicals attach to the next neurone and set up a new electrical impulse
- diffuses across the gap between the 2 synapses
5
Q
What is the iris
A
coloured part of the eye
contains muscles that control size of pupil
6
Q
what is the retina
A
layer of receptors at the back of the eye containing light sensitive cells (rods and cones)
7
Q
what is the ciliary muscle
A
contracts and relaxes to control shape of the lens
8
Q
what are the suspendory ligaments
A
tighten and slacken to change shape of lens
9
Q
what is the lens
A
sits behind pupil and focuses light on the retina
10
Q
What happens in order to focus on a near object
A
- ciliary muscles contract
- suspensory ligaments loosen
- lens becomes thicker/more curved so refracts light rays more strongly
11
Q
What happens in order to focus on a far object
A
- ciliary muscles relax
- suspensory ligaments tighten
- lens becomes thinner/flatter so refracts light rays slightly
12
Q
What is myopia and how can it be corrected
A
short sightedness - far objects are blurred
light focuses in front of the retina
concave lens
13
Q
What is hyperopia and how can it be corrected
A
long sightedness - near objects are blurred
light focuses behind the retina
convex lens
14
Q
What happens in dim light to the eye
A
radial muscles contract
pupil dilates
15
Q
what happens to the eye in bright light
A
circular muscles contract
pupil contracts
16
Q
Can you define homeostasis?
A
The maintenance of a constant internal state!
17
Q
What happens when the core body temperature is too high?
A
- change detected by thermoregulatory centre in the brain by blood flowing around brain
- Vasodilation to increase rate of heat loss because it allows more blood to flow through the skin
- sweating
- The sweat evaporates, transferring heat energy from the skin to the environment
18
Q
What happens when the core body temperature is too low?
A
- change detected by thermoregulatory centre in the brain by blood flowing around brain
- skeletal muscles contract and relax rapidly and we shiver.
- These contractions need energy from respiration, and some of this is released as heat
- Vasoconstriction to reduce heat loss - allows less blood to flow through the skin and conserve the core body temperature
- Hair erector muscles contract and our hair stands on end, trapping a layer of air beneath it to insulate us
19
Q
What happens in the body when blood glucose levels are too high
A
-insulin is released from pancreas
-glucose moves from blood into cells
-excess glucose is converted to glycogen in the liver and muscle cells for storage
20
Q
What happens in the body when blood glucose levels are too low
A
-glucagon is released from pancreas
-glycogen converte to glucose and released into blood
-amino acids/fats are broken down
21
Q
What happens when water concentration in the blood is too high
A
-Less ADH released from pituitary gland
-kidney tubules reabsorb less water
-more (dilute) urine produced (higher conc of water)
22
Q
What happens when water concentration in the blood is too low
A
-More ADH released from pituitary gland
-kidney tubules reabsorb more water
-less urine produced (lower conc of water)
23
Q
How does your body get rid of proteins
A
- broken down into amino acids
- deaminates them in liver
- forms ammonia which is toxic
- converted into urea (also toxic) which can be excreted safely from the body
- the rest of the amino acid molecule can be used for respiration or to make other molecules
24
Q
Describe the process of kidney dialysis
A
- blood is temporarily removed from the patients body
- this is filtered through a dialysis machine
- the patients bood passes over dialysis fluid
- the dialysis fluid has no urea
- urea/waste products diffuse from high concentration in patient’s body to low concentration in fluid
- patient’s blood is returned to their body
25
What is the use of adrenaline
-preparesbody for fight or flight
-increases heart rate
-increases delivery of oxygen and glucose to brain and muscles
-does not involve negative feedback and is secreted from the adrenal glands
26
Describe FSH
-released by pituitary gland
-causes eggs to mature in ovaries
-stimulates ovaries to produce oestrogen
27
Describe LH
-released by pituitary gland
-stimulates release of mature eggs from ovaries (ovulation) around day 14 of the cycle
28
Describe oestrogen
-released by ovaries
-causes lining of uterus to thicken and grow
-inhibits release of FSH
-stimulates release of LH
29
Describe progesterone
-released by ovaries
-maintains lining of the uterus
-inhibits FSH and LH
30
explain the process of IVF
- mother given FSH and LH to stimulate maturation of several eggs
-eggs are collected from mother and fertilised by sperm from father
-fertilised eggs develop into embryos
-multiple embryos are inserted into mother's uterus
31
what are the disadvantages of fertility treatment?
- emotionally and physically stressful
-low success rate
-can lead to multiple births which put the mother and babies at risk
32
What are auxins
- plant growth regulator hormone
- unequal distibution can be seen in phototrophic reactions, causes unequal growth/leaning
Uses as:
- weedkiller
-rooting powder
-promoting growth in tissue cultures
33
What is ethene
- hormone that controls ripening and cell division in plants
Uses as:
- controlling ripening of fruit during storage and transport
34
What are gibberellins
-regulates developmental processes such as seed germination
Uses:
-end seed dormancy
-promote flowering
-increase fruit size
35
Describe adult cell cloning
-The nucleus is removed from an unfertilised egg cell
-The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell
-A very small electric shock stimulates the egg cell to divide (by mitosis) to form an embryo
-These embryo cells contain the same genetic information as the adult skin cell
-When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female (known as the surrogate mother) to continue its development until birth
-Offspring is a clone of original animal
36
Describe embryo cloning
-Egg cells from the best cow are artificially fertilised using sperm cells taken from the best bull
-This forms an embryo
-The developing animal embryo is then split apart many times before the cells of the embryo become specialised
-This forms many separate embryos that are genetically identical
-These cloned embryos are then transplanted into host mothers
-The calves born from these host mothers are all genetically identical
37
What are the advantages of cloning
-Preserve endangered species of plants and animals
-Quickly and cheaply produce commerical quantities of high quality plants year round
38
What are the disadvantages of cloning
-population are genetically similar so are susceptable to disease
-cloned animals are often malformed/have injuries/bad health
-ethics
39
Explain the process of selective breeding
- choose parents with desired characteristics
-breed
-choose offspring with desired characteristics and breed
-continue over many generations until all offspring show desired characteristic
- can lead to inbreeding
- reduces variation in population
40
Describe tissue culture
-Cells are scraped from the parent plant (these cells are known as explants)
-The cells are transferred to a sterile petri dish containing nutrient agar
-Hormones (eg. auxins) are added to encourage plants to grow into small masses of tissue (callus tissue)
-Tissue continues to grow and forms plantlets that can be transferred to individual potting trays and develop into plants
41
Describe cuttings
-An older and more simple method to clone plants (mainly used by gardeners) is by taking cuttings
-Gardeners take cuttings from good parent plants (eg. those that are healthiest and best-looking) – a section of the parent plant with a new bud is cut off
-These cuttings are then planted and grow into genetically identical versions of the original plant
-Plants cloned by taking cuttings can be produced cheaply and quickly
42
Describe genetic modification
-enzymes cut out the desired gene from cell A from an organism
-vector taken out of cell B (usually bacterial plasmid or virus)
-gene is inserted into vector
-this is inserted into a cell - often for production is bacteria so binary fission can take place
-eg insulin collected and purified
-as organism grows, it develops with desired characteristics from gene
43
What are the benefits to genetic engineering
-potential to overcome inherited diseases
-GM crops can have higher yields - higher value crops
-crops can be engineered to be resistant to herbicides/produce own pesticide/drought resistant
44
what are the risks of genetic engineering
-genes fromGM plants/animals may spread into other wildlife and affect ecosystems
-ethical concerns - children
-GM crops are infertile and expensive to buy, not sustainable for smaller farmers/poorer countries to use
-some believe affects of GM have not been fully researched
45
what are the advantages of sexual reproduction
- produces variation in offspring
- offspring may have survival advantage by natural selection
46
what are the advantages of asexual reproduction
- only one parent needed
- time and energy efficient
- faster than sexual reproduction
- many identical offspring can be produced
- successfull traits are always passed on
47
what are the disadvantages of sexual reproduction
- finding a mate and reproducing is time consuming and requires lots of energy
- slow
48
what are the disadvantages of asexual reproduction
- reduced genetic variation, more susceptible to extinction by disease
- harmful mutations would be passed on
49
what is mitosis
the process of producing 2 identical body cells that contain 23 pairs of chromosomes
50
what is meiosis
the process of producing 4 non-identical gametes that contain 23 single chromosomes
51
Explain the process of meiosis
- each chromosome becomes shorter, thicker and more visible.
- the chromatids are joined at the centromere
- nuclear envelope disappears
- spindle fibres come out from each end of the cell and attach to the centronomes of the chromosome
- homologous chromosomes pair up in the centre of the cell
- small parts of the homologous chromosomes cross over. this exchange of genetic material increases variation
- the spindle fibres contract, separating the homologous pair into opposite sides of the cell, which begins to divide. each chromosome is still formed of 2 chromatids
- a new nuclear envelope forms aroud each set of chromosomes and the cell finishes dividing
- each cell has 23 chromosomes
- this happens again and 4 daughter cells are formed with 1 chromosome each, genetically different haploids
52
Describe reproduction in fungi
- some reproduce sexually when conditions are not good
- 2 hyphae from different fungi join and the nuclei fuse so the new hypha has 2 sets of chromosomes
- undergoes meiosis to make haploid spores, making them different from original hyphae
53
Describe reproduction in plants
- plants eg strawberry and spider plats have tiny new plants that form on the end of runners
- can reproduce sexually or asexually
54
Describe reproduction in malaria parasites
- reproduce differently in different life stages
- drop in temperature between human and mosquito triggers sexual reproduction
55
what is a gamete
a specialised sex cell formed by meiosis
56
what is a chromosome
long molecule found in the nucleus of cells formed by dna
57
what is a gene
part of a chromosome that codes for a protein
58
what is an allele
different forms of the same gene
59
what is a genotype
combination of alleles an individual has
60
what is a phenotype
physical expression of the genotype
61
what is DNA made of
a double helix, consisting of two strands of nucleotides
repeating nucleotide units
62
What is in a chromosome
DNA
63
Why did scientists sequence the human genome?
- to understand and treat inherited disorders
- to search for genes linked to different disorders
- to trace human migration patterns from the past
64
what is a nucleotide made of?
- phosphate
- sugar
- one of the four organic bases (A-T, C-G)
- The bases must group together in triplets in order for genes to code for proteins
65
Describe the process of protein synthesis
- DNA double helix is separated
- mRNA is made using DNA strands - transcription (template)
- mRNA leaves nucleus and enters cytoplasm
- mRNA joins onto a ribosome
- mRNA acts as a code for tRNA - translation
- Amino acid on neighbouring tRNA joins together
- A chain of amino acids is a poly-peptide
- The poly-peptide chain folds to form a protein which is used in the cell or exported to the body
66
How do mutations work
- Enzyme almost unchanged so active site is same shape and it works normally
- Active site changed so substrate doesnt fit and enzyme doesnt work
- Active site change shape so a different substrate fits and it catalyses a different reaction
67
What does non-coding DNA do
switch genes on and off
68
What determines the order of amino acids
the order of the triplets
69
What is polydactyly and how is it caused?
- an inherited condition in which a person has extra fingers or toes
- caused by a dominant allele of a gene
70
What is cystic fibrosis
- an inherited disorder of cell membranes that mainly affects the lungs and digestive system
- Become clogged with mucus
- Caused by a recessive allele
71
what is genetic testing
analysis of a person's DNA to see if they carry alleles that cause genetic disorders. It can be done at any stage in a person's life
72
Describe the process of genetic testing
- Antenatal testing before the baby is born
- Neonatal testing on newborn baby's blood
- Pre-implantation, before embryos are implanted in IVF
73
What are the limitations of genetic testing
- False negatives/positives
- Ethical issues
-
74
Describe the process of gene therapy
- identify the gene involved in the genetic disorder
- restriction enzymes cut out the normal allele
- many copies of the allele are made
- copies of the normal working allele are put into the cells of a person who has the genetic disorder due to a mutated or faulty copy of an allele
75
What are problems associated with gene therapy
- the alleles may not go into every target cell
- the alleles may be inserted into the chromosomes in random places, rather than in the required position, so they do not work properly
- some treated cells may be replaced naturally by the patient's own untreated cells, as cells are frequently replaced through the process of mitosis during growth and repair
76
Define evolution
the gradual change in the inherited characteristics of a population over many generations/time
77
Describe the process of natural selection
- Organisms within a species show a wide range of variation
- Individuals with characteristics most suited to the environment are more likely to survive and breed successfully
- These characteristics are passed onto their offspring
78
What is the evidence for evolution
- It has been demonstrated that characteristics are passed onto offspring in genes
- Evidence from the fossil record
- Antibiotic resistance in bacteria
79
What is Darwin's work?
the theory of evolution by natural selection
- Gathered evidence from his worldwide expedition
- All living species evolved from a common ancestor that first developed >3 billion years ago
80
Why was Darwin's work met with hesitation/ only gradually accepted?
- Challenged creationism
- Insufficient evidence at the time of publishing
- Mechanisms of inheritance and variation were not known at the time- only 50 years later
- Other theories such as Lamarckism
81
What are the core theories of Lamarck's theory?
- a characteristic which is used more and more by an organism becomes bigger and stronger, and one that is not used eventually disappears
- any feature of an organism that is improved through use is passed to its offspring
82
Describe the process of speciation.
- 2 populations of the same species are isolated (eg by a river or mountain range)
- Natural selection occurs so that the better adapted individuals reproduce and pass on these different characteristics
- The populations have an increasing number of genetic mutations as they adapt to different environments
- Eventually the 2 populations are so genetically different that they cannot breed to produce fertile offspring.
83
Who is Alfred Russel Wallace?
- best known for his work on speciation
- published joint writings with Darwin on evolution by natural selection
- ‘warning colours’ development
84
What is extinction?
when there are no remaining individuals of a species still alive
85
What can cause extinction?
- New predators
- New diseases/pathogens
- Increased competition for resources or mates
- Catastrophic events/natural disasters
- Changes to the environment
86
Describe how a fossil is formed
- Reptile dies and falls to ground
- Flesh decays, leaving skeleton to be covered in soil and clay before it is damaged
- Over millions of years, the skeleton becomes mineralised and turns to rock
- Eventually, the fossil emerges as the rocks move and erosion takes place
87
What can a fossil be formed from?
- parts of an organism that do not decay as one or more of the necessary conditions arent present
- Hard parts of an organism are replaced by minerals
- Preservation of traces of organisms (eg burrows or footprints)W
88
What are the benefits of the fossil record?
- Can tell scientists how individual species have changed over time
- Fossils allow us to understand how life have developed over Earth's history
- Fossils can be used to track the movement of a species or its ancestors across the world
89
What are the problems of the fossil record?
- Many early organisms were soft-bodied and decayed before producing fossils
- Gaps in fossil record as not all fossils have been found/ some have been destroyed
90
Who developed the 3 domain system
Carl Woese
91
Who developed the classification system?
Carl Linneaus
92
What is the classification order?
Kingdom
Phylum
Class
Order
Family
Genus
Species
93
What are the 3 domains
Archaea - Primitive bacteria in extreme environments
Bacteria
Eukaryota
94
What is the binomial naming system?
*Genus species*
95
How does antibiotic resistance take place?
- Full course of antibiotics isnt taken
- Small amounts of bacteria are resistance
- Resistant bacteria grow and reproduce
- Non-resistant bacteria stop growing/reproducing and are killed
- All bacteria are now resistant
96
Who helped to develop our understanding of genetics?
Gregor Mendel
97
How did Gregor Mendel develop our understanding of genes
breeding yellow and green peas
- Each characteristic is determined by units that are passed on unchanged to offspring
98
Why did many scientists not accept Mendel's work?
- Many people believed in blended inheritance
- His work was published in an obscure journal where not many people saw it
- He was a monk, not a scientist
99
How was gene theory developed?
- Late 19th century chromosomes were observed during cell division
- Early 20th century genes and chromosomes were observed to have behaved similarly - idea that genes are located on chromosomes
- mid 20th century structure of DNA and mechanism of gene function were determined
100
What is a population
the total number of organisms of the same species that live in one specific geographical area
101
What is a community
group of 2 or more populations of different species living in one specific geographical area
102
What is an ecosystem
the interaction of the abiotic and biotic aspects of an environment
103
What is interspecific competition
Competition between organisms of a different species
104
What is intraspecific competition
Competition between organisms of the same species
105
What is a stable community
a community where all of the species and environmental factors are in balance so that population sizes remain fairly constant
106
Describe the interaction between a predator and a prey population
- Population of prey increases so there is a larger food supply for predator
- More predator offspring survive
- Larger numbers of predators kill more prey
- Less predators can be sustained
107
What is a biotic factor
the living factors in an ecosystem
108
What is an abiotic factor
the non-living factors in an ecosystem
109
What are some factors that would negatively affect the biotic parts of an ecosystem
- decreased availability of food
- new predators
- new pathogens
- competition
110
What is an adaptation?
A feature that an organism has that helps it survive in the environment it lives in
111
What is a structural adaptation?
a physical feature that allows an organism to successfully compete
- Sharp teeth
- Camouflage
112
What is a behavioural adaptation?
the behaviour of an organism that gives it an advantage
- making nests to attract a mate
- courtship dances
113
What is a functional adaptation?
an adaptation related to processes that allow an organism to survive
- photosynthesis
- production of poisins or venom
114
What is an extremophile
organisms that can live in environments where most other organisms cannot survive
115
What is a deep sea vent
environments with very high pressure and temperatures, no sunlight and a lot of acidity
116
Cacti adaptations
- spines to reduce surface area and therefore water loss and to deter predators
- Long roots to reach water underground
- Waxy cuticle to prevent water loss
117
Camel adaptations
- Feet with large surface area to distribute weight and stop sinking into sand
- Hump stores of fat to provide energy when food is scarce
- Tough mouth and tongue to allow camel to eat cacti
- Long eyelashes to keep sand out of eyes
118
Polar bear adaptations
- White fur to camouflage when hunting prey
- Feet with large surface area to distribute weight and stop sinking into snow
- Small ears to prevent heat loss
- Thick fur for insulation
119
What is a producer?
An organism that produces its own food via photosynthesis
120
What is a consumer?
Primary - organisms that eat producers
Secondary - organisms that eat other consumers
121
What is an apex predator?
carnivores with no predators
122
What is the trophic level of an organism
the number of steps it is from the start of the food chain
123
How much biomass is transferred from one trophic level to the next
10%
124
What is biomass?
living or dead biological/organic matter
125
Why is biomass lost between trophic levels?
- Use in life processes eg respiration
- Some matter is excreted as waste products eg faeces and urine
- Energy is used in movement and to keep animal warm
- Not all of an animal/plant is ingested (eg fur, roots)
126
Explain the carbon cycle
- Organic compounds in dead organisms
--due to dying animals - organic compounds in consumers
- Carbon compounds in fossil fuels
--decay and decomposition - CO2 released as microorganisms respire
--combustion
- CO2 in air and dissolved in water/oceans
--photosynthesis removes CO2 from environment
- Organic compounds in green plants
--die and are fed to living animals
--respiration returns CO2 to the atmosphere
127
Explain the water cycle
Precipitation - as water droplets in clouds get heavier they fall as rain/snow/hail
Percolation - water trickles through gaps in soil and rocks
Transpiration and respiration - loss of water vapour from plants and animals directly to the atmosphere
Evaporation - the sun heats the earth's surface and water is turned from a liquid into water vapour
Condensation - as moist air rises it cools and condenses into liquid water droplets producing clouds
128
How do decomposers decompose organic matter
- break down dead plant and animal matter by secreting enzymes into the environment
- small soluble food molecules produced then diffuse into the decomposer
- These materials are cycle through an ecosystem by decomposers returninf carbon to the atmosphere as carbon dioxide and mineral ions to the soil
129
Describe the decay cycle
- producers
- plant material eaten by consumers
- living organisms
- death, exrection, faeces and urine
- decomposers break down dead bodies and waste materials
- mineral ions into soil
- carbon dioxide into air
- carbon dioxide into plants via photosynthesis, mineral ions (nitrates) into plant via roots
130
What conditions are needed for decay
- oxygen
- moisture
- warm temperature
- neutral pH
131
What happens to decay when there is a lack of oxygen
happens anaerobically
methane gas produced
- can be used in biogas generators to use as a fuel
132
Why do gardeners/farmers need decomposers
act as fertilisers
133
How might a temperature change affect the distribution of species
- migrate seasonally away/towards equator to get to milder conditions
134
How might availability of water change affect the distribution of species
during a drought animals might have to move from their usual habitats to areas with more water
135
How might composition of atmospheric gases change affect the distribution of species
human activities release greenhouse gases and pollutants which create harmful effects like climate change and acid rain.
136
What is biodiversity?
- the variety of all the different species of organisms on earth or within a specific ecosystem
137
How does high biodiversity affect an ecosystem?
- ensures stability
- as it reduces the dependance of one species on another for food
138
How to maintain biodiversity
- breeding programmes in zoos for endangered species
- protection and regenerations of rare habitats
- reintroduction of hedgerows in monoculture farmland
- government policies to reduce deforestation and CO2 emissions
- recycling
139
Land pollution
- non-recyced rubbish in landfill - toxic chemicals can seep into soil, takes up a lot of land, plastic stays on earth
- fly-tipping
- toxic chemicals - (pesticides/herbicides) cannot be broken down by organisms and can be absorbed into plants and build up into their tissues (bioaccumulation). This will accumulate increasingly on each trophic level and lead to dangerous levels in the consumers (biomagnification)
140
Water pollution
- toxic chemicals - bioaccumulation and biomagnification
- untreated sewage - eutrophication (good food source for bacteria, which then divide rapidly and respire, taking oxygen from plants and animals)
- fertilisers - eutrophication (cause to algae bloom, good food source for bacteria)
141
Air pollution
- combustion of fuels with impuritites releases sulfur dioxide
- nitrogen oxides produced during fossil fuel combustion
- these react with oxygen and dissolve in rainwater to form acid rain
- acid rain can destroy plants
- can make bodies of water more acidic, unsuitable for the plants and animals
- leaching of minerals that eg aluminium that are toxic to fish
142
What are the consequences of growing population
- more land is used
- more resources used
- destruction of peat bogs to produce garden compost
--> destroyed for garden compost or fuels (CO2 released)
--> destroys habitat and biodiversity
143
What has deforestation resulted in
- large amounts of CO2 being released into atmosphere
- extinction and reductions in biodiversity as habitats are destroyed
- climate change increased
144
What is food security
having enough food to feed a population
145
What are biological factors threatening human food security
- rapid population growth and increasing birth rates
- changing diets in developed countries requiring scarce foods to be trasnported globally
- new pests and pathogens impacting farming of vast amounts of crops
- environmental changes eg drought affecting food production
- increasing cost of agricultural inputs like fertilisers
- conflict
146
Ways to fish sustainably
- smaller nets/ bigger holes in nets
- fishing quotas by government
147
What is intensive farming
farming techniques that make food production more efficient by restricting energy transfer from food animals to their environment
148
examples of intensive farming
- limiting movement of animals
- controlling temoerature of animals surroundings
149
advantages of intensive farming
- high yield and quicker growth of crops and animals
- efficient use of food and less waste produced
- can meet demand for food for a rapidly increasing population
150
disadvantages of intensive farming
- increased risk of antibiotic resistant bacteria strains
- pesticides and herbicides may kill beneficial organisms and reduce biodiversity
- ethical issues about animal warfare and quality of life
- large carbon dioxide and methane emissions
151
how to maximise yield from animals and plants
- feed animals high-protein foods to increase growth
- give animals antibiotics to prevent or treat disease
- regularly use fertilisers, herbicides and pesticides on crops
152
What biotechnology can be used to increase food production?
- microorganisms can be cultured for food
--> mycoprotein is a protein-rich vegetarian food harvested and purified from Fusarium on glucose syrup in aerobic conditions
- GM crops have higher yields, increased resistance to changes in environment or improved nutritional values (golden rice)
- Bacteria can be GM to produce human insulin which can be harvested and purified for diabetes treatment
153
what is global warming?
the gradual increase of average temperature of the earth
154
what has global warming resulted in?
- large scale habitat change and reduction causing in reduction in biodiversity
- extreme weather and sea level changes
- migration of species to different parts of the world affecting ecosystems
- threats to the security and availabilty of food
155
Definition of tissue culture.
A group of cells that are grown into a new organism
156
Describe how carbon and nitrogen compounds in dead leaves are recycled by living trees. [6 marks]
- Decomposers such as bacteria release an enzyme to break down/digest dead organic matter such as leaves
- The decay of the leaves releases nitrate ions
- These are taken up by tree roots via active transport and can be used to make proteins and amino acids via proteinsynthesis
- Decomposers/microorganisms respire as they do this, releasing CO2
- This is taken in by the stomata on the leaves for/by photosynthesis in order to grow and produce glucose which can be stored as cellulose to strengthen cell walls
157
Farming techniques have changed in recent years.
Describe:
* why more land is being used for farming
* how increased farming has decreased biodiversity
human land use
* increasing population requires more food
* crops / livestock for food
* farming crops for biofuels
* peat use as compost
* peat use as fuel
* increased use of pesticide / insecticide / herbicide / fertilisers
* use of free-range / organic methods increases land use (for
same yield)
link to biodiversity
* deforestation
* monocultures
* loss of hedgerows (to make fields larger)
* loss of habitat
* consequence of loss of habitat eg (change in) migration
* fertiliser run off polluting water
* use of pesticide / insecticide / herbicide reduces insects / plants
which damages food chains
* more soil erosion
link to atmospheric pollution
* more carbon dioxide (from farm animals / machinery)
* more methane (from cows)
* climate change or global warming
* example of impact on biodiversity
* acid rain
* desertification
