Download Photosynthesis

Higher Biology
Unit 3:
Sustainability and
Interdependance
Pupil Notes
 Key Area 3.1 a Food Supply
Food security is the ability of a population to access food in
sufficient quality and quantity to maintain a healthy population.
Why is food security an increasing issue in the human population?
What is meant by sustainable food production?
Revision
Only around 10% of the energy from one tropic (feeding) level is available to
the next.
Producer
Primary
consumer
Secondary
consumer
Tertiary
consumer
Since energy is lost a t each trophic level, keeping animal livestock can lead
to less food production per unit of land.
Name one way in which energy is lost at each trophic level:
Explain this statement; energy is lost from the food chain as waste, but not
from the food web.
 Key area 3.1b Plant growth and productivity
What happens when light reaches a leaf?
Absorption Spectrum
Absorption Spectra
When a beam of light is passed through a prism , the
spectrum
of white light is produced
When a beam of white light is passed through a sample
of leaf pigments and then passed through a prism, an
absorption spectrum is produced.
Each black band is a region of the spectrum where
Light energy has been absorbed by the leaf pigments
Why plants have more than one pigment?
Points to note:
 There is never a point where NO photosynthesis is
occurring.
 Little / Less photosynthesis occurs at other
wavelengths of light.
 Other pigments are required to allow
photosynthesis at a WIDER RANGE of light
wavelengths.
Chromatography
Chromatography is a technique used to separate the
components of a mixture which differ in their degree of
solubility in a solvent.
The more soluble the component the higher it is carried up
the paper
Most soluble
carotene
xanthophyll
Chlorophyll a
Least soluble
Design feature/Precaution
Fine sand used
Chromatography paper doesn’t
touch the sides of the tube
Spotting and drying done many
times
Pigment spot above solvent
line
Equation to calculate Rf Value:
Rf Value =
Chlorophyll b
Reason
The Chemistry of Photosynthesis
There are two enzyme controlled stages in photosynthesis
1: Photolysis, which takes place in the Grana ( Granum ) of the chloroplast
2: Carbon Fixation, which takes place in the Stroma of the chloroplast.
The chloroplast has a double membrane.
Photosynthesis
Light energy
Carbon dioxide + water
Glucose
+
Oxygen
Chlorophyll
Starch
(storage)
Cellulose
(structural)
1) Light Dependant Stage
Takes place in the granum of the chloroplast
Light
Trapped by _____________
Splits ________
_________ (by-product)
NADP
NADPH2
ADP + ___
ATP
_________________
Transfer of high energy electrons through electron transport chain
releases energy to make ATP & split water
 What traps the light energy?
 What is water split into?
 Describe the role of ATP Synthase
 What two useful products are used in carbon fixation?
 What is the by-product of the light dependant stage?
2) Carbon Fixation
 Takes place in the ______________ of the chloroplast.
 During this stage the carbon dioxide is ___________ to glucose.
Also called
• A) ___________ ______________
• B)light independent stage
• C) dark reaction
Requires
1. ATP (photolysis)
2. NADPH2 (photolysis)
3. ______________ _______________ (diffusion into stomata from air)
Complete the following diagram. It is the same as the previous page, but
with a 90 degree rotation:
3PG - 3Phosphoglycerate
Intermediate
Rubisco
enzyme
Carbon dioxide
(3C)
Ribulose BiPhosphate (5C)
Glucose (6C)
Starch
(storage)
Cellulose
(structural)
Other molecules of carbohydrate produced by photosynthesis can be
passed onto other pathways. These can contribute to the production of
amino acids, protein and nucleotides.
Questions
1) State the two fates of glyceride – 3 – phosphate
2)
Name the enzyme involved in the reaction between RuBP and CO2.
Questions
Limiting factors
A limiting factor is any factor that is restricting the rate of photosynthesis.
The rate of photosynthesis is usually measured by the number of
_________ bubbles produced or the _______ of food produced.
 The limiting factor at A is: ______________________
 The limiting factor at B is: ______________________
 The limiting factor at C is: ______________________
At point D the rate if photosynthesis may have levelled out for 2 reasons:
1)
2)
Limiting Factor Question
The concentration of carbon dioxide in the atmosphere can affect the rate
of photosynthesis.
The investigation using Cabomba can be adapted to show how the rate of
photosynthesis varies with different concentrations of carbon dioxide when
all other factors are kept constant. The table shows the results from an
investigation carried out this way.
Concentration of carbon dioxide
Rate of photosynthesis (oxygen
(%)
bubbles per min)
0.0
0
0.1
2
0.2
4
0.3
8
0.4
8
0.5
8
Plot the results of the investigation as a line
graph.
1. Label the part of the graph over which the rate of photosynthesis is
rising with an R.
2. Label with an S the part of the graph where increasing the carbon
dioxide concentration has no effect on the rate of photosynthesis.
3. Why is there no photosynthesis when there is no carbon dioxide?
4. Why can carbon dioxide only be described as a limiting factor in part
R of your graph?
5. What factor might be limiting the rate of photosynthesis in part S of
the graph?
Limiting Factor Question
Plant Productivity
 Productivity is the rate of generation of new biomass per unit area
per unit of time and is controlled by the rate of photosynthesis.
Biomass
 Biomass is defined as the total mass of all organic material within a
population of plants
 Biomass is measured as increase in _______ _________ due to
variable water levels in fresh mass.
Assimilation
 Assimilation is the process where food produced by photosynthesis is
converted into complex cell constituents like the cell wall.
 Net assimilation= photosynthesis - ___________
 The units of measurement of Assimilation are increase in dry
mass/unit area/time.
Productivity depends on:
• Arrangement
• Shape
• Number of leaves
Maximum surface area of leaves & minimum shading of lower leaves
Harvest Index
=
Dry mass of economic yield
Dry mass of biological yield
 The Harvest Index can be worked out by dividing the dry mass of
economic yield by the dry mass of biological yield.
1) Biological Yield of Crops - Total plant biomass ---(mature barley
plants)
2) Economic Yield of Crops - Mass of desired product (barley grain)
Question
 Key area 3.2 Plant and Animal Breeding
New & improved plant crops can be improved by manipulation of heredity
to have higher yields, higher nutritional values and improved resistance to
pests and diseases.
Continuous variation is controlled by more than 1 allele (polygenetic
inheritance). Examples of polygenetic inheritance include birth/weaning
weight of cattle.
Outbreeding means –
Inbreeding means -
Testcross / Backcross
If the undesired allele is recessive, heterozygous individuals can be found
using a testcross or ___________
Draw out the crosses using the homozygous recessive and the two possible
genotypes for dominant phenotype. Use this to explain how the backcross
works.
P
BB x bb
P
Bb x bb
Gametes
Gametes
Punnets Square
Punnet Square
b
F1
All dominant
F1
½ dominant,
½ recessive
Explanation
By looking at the offspring you can tell what the unknown dominant
phenotype parent was passing on. Since the recessive parent could only
be passing on the recessive allele.
As inbreeding continues inbreeding depression can occur due to
______________________________________________________________
______________________________________________________________
______.
How is inbreeding depression avoided by;
Self-pollinating
plants
Outbreeding
species
Cross breeding and F1 hybrids
Introducing new alleles into a population can be achieved by crossbreeding
(different breeds in animals, or different cultivars in plants)
There are two main ways to maintain the ‘new’ breed. Give an advantage &
disadvantage
F1 hybrids are often used in plant breeding.
Describe what is meant by hybrid vigour.
Why is the F2 generation not as useful as the F1.
Explain how each of the following genetic technologies have been (or
could be) used in breeding
Genetic
transformation
Genome
sequencing
 Key area 3.2 Crop protection and animal welfare
Crop protection
Crop weeds
 Weeds, pests and disease populations compete with crops and
reduce biodiversity
 Properties of annual weeds are rapid growth, short life cycle, high
seed output and long-term seed viability
 Perennial weeds have competitive adaptations like storage organs
and vegetative propagation
Invertebrate pests
 Most pests of crop plants are invertebrates like
1. Nematodes
2. Worms
3. Molluscs
Disease of crop plants
 Plant diseases can be caused by fungi, bacteria or viruses – often
carried by invertebrates
Control methods
Cultural - ploughing, removing weeds early and crop rotation
Chemical
a) Selective - overstimulate plant metabolism and exhaust food
reserves
b) Contact – non selectively destroys green plant that it comes into
contact with
c) Systemic – absorbed by weed and transported internally
Selective
Contact
Systemic
Herbicides
Pesticides
Fungicides
 Disadvantages of chemical control are that they can be persistent,
they can accumulate and they are not specific
Biological control - reduces pests by introducing a predator, parasite or
pathogen
 Disadvantages of biological control are that not all pests may be killed
or a predator could become a pest if their populations rise
Integrated pest management is the combination of chemicals and
biological control
Animal Welfare
Behavioural indicators – explain what each is (use examples if useful) and how it
can indicate poor welfare
Stereotypy
Repetitive behaviours, may be natural but out of
context.
e.g.
Misdirected
behaviour
A natural behaviour that is directed against e.g.
another animal
e.g
Failure in sexual
behaviour
Natural pattern of sexual behaviour either in terms
of partners or timing or action does not happen
Failure in
parenting
behaviour
Especially in mammals, where normal parenting
behaviours and lack of care occur. This can lead to
the offspring not thriving or even dying. Or the
offspring also exhibiting abnormal behaviours
Altered levels of
activity
From lack of activity where expected to increased
activity
e.g
Ethology Ethogram -
The observation and study of animal behaviour
Illustration e.g pie chart of the results of animal
behaviour studies.
Preference testing – an animal is given a choice of two condition to
determine which condition they prefer.
 Key area 3.5, 3.6 Symbiosis, social insects and social
behaviour
 Symbiosis (living together) is a close ecological relationship between
the individuals of two (or more) different species.
 Sometimes a symbiotic relationship benefits both species, sometimes
one species benefits at the other's expense, and in other cases neither
species benefits.
 Ecologists use a different term for each type of symbiotic relationship:
Mutualism -- both species benefit
Example –
Parasitism -- one species benefits, the other is harmed
Example -
Describe the thinking behind the proposal that chloroplast and
mitochondria have a symbiotic origin:
Parasitism example
The diagram below is taken from www.cdc.gov and shows the life cycle of
the protozoan that causes African Trypanosomiasis, or sleeping sickness.
Question
Social Hierarchy
 some are dominant and some are subordinate/submissive (not
strongest/weakest) – it is a pecking order system
 dominant/leader/alpha/highest ranking/highest in hierarchy eat
first/get more/best food (not strongest/weakest)
 The advantage of dominant hierarchy are: a) Real aggression is minimised
b) Energy is conserved
c) Experienced leadership is guaranteed
d) The largest and strongest males survive and breed with the
strongest females, passing on their genes to the next
generation.
e) Subordinate members gain more food than if alone
Describe an example:
Cooperative hunting
 More food / energy gained than if hunting alone
 increases success rate OR more chance of catching prey
 less energy used/lost (not wasted) per individual (than by hunting
alone)
 Large/larger prey obtained/caught/killed (not hunted)
Describe an example:
Social defence



Groups act together to defend or raise alarm
Safety in numbers
Weaker members have increased survival chance
Describe an example:
Altruism
Animals usually show behaviours which are beneficial to their own chances of
survival. In some cases an animal will behave in a manner which is harmful to itself
but beneficial to another individual. This behaviour is described as altruism. An
example of altruism can be seen in wolves which bring meat back to members of
the group who were not present at the kill. The “donor” wolf must expend energy
carrying the kill back and the “recipient” wolf benefits as it gains access to food.
Reciprocal altruism
Reciprocal altruism is a behaviour whereby an organism (donor) acts in a manner
that temporarily reduces its fitness while increasing another organism's (recipient)
fitness with the expectation that, the roles of donor and recipient later reverse.
Example : Grooming in primates can be thought of as an example of reciprocal
altruism. An individual will expend time and energy grooming another member of
the group in the expectation that the favour will be returned in the future.
Kin Altruism
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 terms of the increased
chances of survival of shared genes in the recipient's offspring or future offspring.
Example :Bee colony structure
In the honey bee colony the queen is solely responsible for laying eggs, the drones
for fertilising her, and the workers for gathering food and performing sundry duties
in the hive. Each rank is adapted for its particular job: thus the queen is the fertile
female, the drones fertile males, and the workers sterile females with welldeveloped mouth parts and other structural adaptations for collecting nectar and
pollen.
The importance of social insects as a keystone species
Social insects live in colonies. There is a division of labour, where some can
carryout reproduction whilst others are collecting food.
The feeding of an individual involved in reproduction by those collecting the
food would be an example of kin selection.
Social insects are often keystone species within their ecosystems. This
means they are of critical importance to the ecosystem and their removal
could cause the ecosystem to collapse.
Some insect species are of economic importance to humans providing
ecosystem services such as pollination and pest control.
Complete the following diagram using pg130 in your textbook
Keystone
species
Primate Behavior
Complete the following diagram using pg307-310 in your textbook
Reduce conflict
- appeasement
Parental Care
Reduce conflict ritualistic display
Social Status
Social Structure
Essay example:
Write notes on social behaviour within primates (5)
Where do you get the marks?
1) primates have a long period of parental care / spend a long time with their
parent(s)/ look after young for a long time
1
2) this gives opportunity to learn complex social skills
1
3) primates use ritualistic display / appeasement (behaviour) to
reduce conflict/aggression / ease tension
1
4) any one example of appeasement / alliance forming / ritualistic behaviour
e.g. grooming / facial expression / body posture / sexual presentation 1
5) second example of appeasement / alliance forming / ritualistic behaviour 1
6) individuals form alliances which increase social status OR Social hierarchy
exists 1
7) complexity of social structure is related to ecological niche / resource
distribution / taxonomic group
1
 Mass Extinction and biodiversity
Mass extinction is the complete demise of a group of organisms.
After extinction events, biodiversity can increase again due to speciation.
Extinction rate is much higher due to the rate of ecosystem degradation
which is caused by human intervention.
Total variation that exists among living things on Earth depends on
number, complexity of structure and genetic variation
Biodiversity can be measured in three ways: genetic diversity, species
diversity and ecosystem diversity
 Genetic diversity -
 Species diversity -
 Ecosystem diversity -
 Island biogeography is the study of factors that affect the biodiversity
on an island
 A true island is permanently surrounded by water
 A habitat island is an area surrounded by an unlike ecosystem
 Threats to biodiversity
Exploitation
 Exploiting a natural resource means to make the best of it
 Overexploiting a species is to remove and use up faster than the
species can reproduce
 After overfishing, quotas were introduced and the number of boats
were limited to recover biodiversity
 Recovery after overexploitation doesn’t always happen
Bottleneck Effect
 An event that can wipe out a significant proportion of the population
is a bottleneck event. (e.g. flood, earthquake)
 Bottleneck events lead to the bottleneck effect – this could decrease
the chance of genetic variation
Fragmentation
 Fragmentation is the formation of several habitats whose surface
area is less than the original habitat.
 Fragmentation can happen when forests are cleared for agriculture,
housing, motorways etc.
 A habitat corridor is a narrow strips of quality habitat to link
otherwise isolated habitats
Introduced, naturalised and invasive species
 Introduced species – non native species which has been added
intentionally or accidently to a new geographical position.
 Naturalised species – This introduced species may become
established in this new location
 Invasive species – can spread rapidly and outcompete or prey on the
native species
Question
Greenhouse gases – e.g carbon dioxide and methane
 reflect infrared radiation back to Earth to keep it warm thus causing
Global Warming.
 as the population increases, the average energy use increases. This
increases the concentration of gases in the atmosphere. This is
anthropogenic climate change (man-made)
Climate change
 Climate change forces species to move their range and favours
generalist species over specialist species
 Generalists can tolerate a wide range of climates and adapt quickly to
change
 Specialists are specialised to life in a specific ecosystem. They can’t
adapt or move their range and may face extinction
 Climate change could result in communities being dominated by
generalists, leading to a loss in biodiversity
 Climate change modelling is when a computer simulates interactions
between factors that affect and are affected by climate. This is useful
but hard to predict.