Topic 5 Ford Flashcards
What is photosynthesis used for?
- growth as it can make new molecules e.g. DNA, proteins, cellulose
- respiration as it releases glucose and energy within glucose that can be used for other reactions
- stored as starch
What are the two main stages of photosynthesis?
the light dependent reactions and the light independent reactions (Calvin cycle)
Phosphorylation
adding phosphates to a molecule
Lysis
splitting up/ breaking
Synthesis
making something
Photo
light
Hydro
water
What is ATP?
Adenosine Triphosphate - is the universal energy transfer molecule in a cell
Uses of ATP:
- active transport
- respiration (glycolysis)
- anabolic processes
- movement: muscle and spindle action
Oxidation
loss of electrons - lose hydrogen releasing energy
Reduction
gain of electrons - gain hydrogen absorbing energy
Redox reactions
a series of reduction and oxidation reactions
What is the co-enzyme used in photosynthesis?
NADP (P –> Photosynthesis)
What is the purpose of NADP?
its job is to carry hydrogen
Why are leaves green?
Leaves are green because with white light all are blocked apart from green light which is reflected. Leaves turn red/ orange/ yellow in Autumn because the chlorophyll is being broken down into other pigments so you see other colours
What are pigments?
substances that absorb visible light - chloroplasts contain a mixture of different pigments
Where are chlorophyll molecules found in the chloroplast?
in the photosystems in the membranes
What is a photosystem?
a group of light absorbing pigments
Where do the light dependent reactions happen?
in the Thylakoid membrane
Where do the light independent reactions happen?
in the stroma
Overview of light dependent
- light strikes chlorophyll
- 2 electrons are excited
- 2 electrons move along the electron transport chain in a series of redox reactions
- the energy released from this turns ADP + Pi –> ATP
- water undergoes photolysis causing 2 electrons to replace the ones in the photosystem
- hydrogen from the water and electrons from transport chain are used to reduce NADP
- oxygen is a waste product
Overview of light independent
- carbon dioxide combines with RuBP
- this is catalysed by RuBISCO and forms a 6 carbon compound
- this is unstable so immediately breaks down to form two 3 carbon compounds of GP
- the 3 carbon compound GP turns into GALP by using energy (a phosphate) from ATP and the hydrogen from NADPH
- some of the GALP can be removed to make hexose sugars and other organic molecules and the rest will continue in the cycle to be rearranged to form RuBP again
Why is light independent reactions a better term than dark reactions?
because they can happen in the light and the dark (unlike the light dependent - only in light)
What is carbon fixation?
when carbon dioxide combines with RuBP to form GP
What would happen to the Calvin cycle if a plant was denied light?
it would continue as normal until a point when the light dependent reactions can’t happen anymore, once the light dependent stops the Calvin cycle will stop as their will be no ATP or NADPH - nothing happens to RuBP and GP levels
What will happen if CO2 levels fall?
the GP levels will fall and RuBP levels will rise as it stays constant but less is being used to make GP but GP is turning into GALP
What factors affect/ limit photosynthesis? How?
- temperature - can denature the proteins
- light intensity - can affect the light dependent reactions so more/less ATP and NADPH being made and available for use
- CO2 concentration - affects the Calvin cycle
What organic substances can the Calvin cycle be the starting point for?
- hexose sugars
- starch
- lipids (fatty acids from GP)
- proteins (some amino acids can form from GALP)
Chlorophyll only…
…absorbs certain wavelengths
Why does not all light reaching Earth hit plants?
some will hit buildings
How much of light reaching the plant is absorbed?
40%
What happens to light (energy) reaching the plant?
- reflected
- pass straight through
- absorbed
- energy not absorbed by chlorophyll but used in evaporating water from leaves
GPP - Gross Primary Productivity
the rate at which energy is taken in into organic molecules (e.g. glucose)
energy per area per year - Jm-2y-1
NPP - Net Primary Productivity
the rate at which energy is transferred into the organic molecules that makes up the new plant biomass
Efficiency of Photosynthesis =
(GPP / amount of light striking the plant) *100
NPP =
GPP - R
Succession
- the change in one ecological community to another over time
- the gradual change in a community over time
Habitat
a place with a distinct set of conditions where an organism lives
Population
a group of individuals of the same species found in an area at that time
Community
different populations sharing a habitat/ ecosystem at a particular time
Primary succession
formation of a habitat where no community has been before - bare rock, sand, open water (occurs when organisms colonize a lifeless habitat)
Secondary succession
when an existing community has been cleared - fire, tsunami, war, ploughed field (occurs when organisms recolonize a devastated ecosystem)
Pioneer species
the first organisms to colonise a habitat
Climax community
a stable community that remains unchanged
Deflected succession
takes another route along succession so it doesn’t reach its climax community - often human activity preventing succession running its course
Why can only a few pioneer species colonise the sand?
- lack of nutrients
- salinity, high salt
- pH, alkaline
- wind, sand moves
- dry conditions
As you move from the sand dunes to the woodland what happens to animal diversity? Why?
the animal diversity increases, this is because there is less extreme conditions and they’re able to create more niches
Why do pioneer species not end up in the climax community?
because they don’t have adaptations for it and can’t compete very well
What happens to the species richness and species diversity in a climax community?
the species richness - increases as increased biodiversity
the species evenness - normally one dominant species so not very even
What happens during succession?
The organisms within an ecosystem change its abiotic conditions. The better adapted organisms colonize the area, replacing current inhabitants
Interspecific
between different species (Internet - everyone)
Intraspecific
between the same species (Intranet - school network)
Pioneer community features
- harsh environment
- extreme abiotic conditions
- poor competitors
- low organic matter (living things)
Climax community features
- high species diversity
- little tolerance of abiotic extremes
- stable environment
- good competitors
High stress
exposure to difficult conditions
How could you sample species distributions with an environmental gradient? Random
Stratified random sampling - dividing the area into strata on the basis of obvious variation within it such as vegetation changes, fixed distances, fixed heights. Within each strata random sampling by x,y co-ordinates or random walking
How could you sample species distributions without environmental gradient? Random
Grid method, a grid is laid out and random numbers are used as x,y co-ordinates. Alternatively, pacing the random numbers can be done from a fixed starting point
How could you sample species distributions with an environmental gradient? Systematic
Transect - A line transect, sampling may be continuous or interrupted along the line. Continuous belt transect, rolling a quadrat over measuring everything along the transect length. Interrupted belt transect, quadrats set out at regular intervals
Environmental gradient
a gradual change in an abiotic factor e.g. light intensity, pH, salinity, soil moisture
How could you sample species distributions without environmental gradient? Systematic
Grid method, a grid is laid out and data is recorded at regular intervals across the grid
Qualitative recording
presence or absence of species in a quadrat
Quantitative recording
- Density
- Percentage cover
- Frequency
Density recording
density is a count of the number of individuals of a species per unit area
Frequency recording
frequency is the probability or chance of finding a species in a given area - divided quadrat - presence or absence is recorded for each species in a sub-unit
Percentage cover
- direct estimate with an open quadrat
- Scales: Braun-Blanquet, Domin, ACFOR
- Divided quadrat: estimate the number of squares a species would fully occupy
- Point quadrat: number of hits *10
Why does algae look different colours?
Because in water different wavelengths of light pass through them. All photosynthesise and different pigments are picked out and used depending on the water so different colours are made
