Biology topic 5

what is an ecosystem

A community of organisms in conjunction with nonliving factors EG rainfall

Community 

The various populations found in an area

Population

a group of individuals of a single species

Habitat

an area with distinct set of conditions where an organism lives

Abiotic factors

non-living physical and chemical components of an environment that influence the distribution, survival, and growth of living organisms

biotic factors

all the living components of an ecosystem that shape, influence, and interact with other organisms

List the biotic factors that can affect the numbers and distribution of species in an ecosystem 

interspecific, intraspecific competiotion, predation

List the abiotic factors that can affect the numbers and distribution of species in an ecosystem

air/soil temp, rainfall, humidity, disolved oxygen sensor, light intensity, aspect, slope, soil compction, soil/water PH, soil water content

the two sampling techniques that can be carried out in an ecological study

systematic and random

how to determine which method is appropriate based on the area of study (give examples) 

Systematic Sampling

Use when there is a clear environmental gradient.

• Why: Shows how species change across the gradient.

• Example: Plant distribution from shore → inland along a transect.

Random Sampling

Use when the area is uniform with no obvious pattern.

• Why: Avoids bias and gives a representative sample.

• Example: Estimating clover cover in a uniform grass field.

a valid and reliable method for carrying out systematic sampling 

• Lay a transect line across the environmental gradient.

• Place quadrats at regular intervals (e.g., every 2 m).

• Use the same quadrat size and same measurement technique each time.

• Keep conditions consistent (same observer, time of day).

• Repeat the transect multiple times to improve reliability.

a valid and reliable method for carrying out random sampling

• Divide the study area into a grid using tape measures.

• Use a random number generator to select grid coordinates.

• Place quadrats at the randomly chosen points to avoid bias.

• Use the same quadrat size and same measurement technique each time.

• Keep conditions consistent (same observer, time, weather).

• Take many samples to increase reliability.

how a frame quadrat can be used to estimate percentage cover of a species

• Place the frame quadrat randomly or systematically in the study area.

• Look at each square within the quadrat and judge whether the species is present.

• Count how many squares contain the species.

• Calculate percentage cover:

Percentage cover=Number of squares with speciesTotal squares×100

• If squares are not marked, estimate visually what proportion of the quadrat is covered.

how a frame quadrat can be used to calculate species richness

• Place the frame quadrat randomly or systematically in the habitat.

• Identify every different species present inside the quadrat.

• Count the number of distinct species (not abundance).

• Repeat in multiple quadrats and calculate the mean species richness.

when it would be appropriate to use a student t test stats analysis. Give a couple of examples 

compareing two mean values

how you would correctly write a hypothesis for the student t test 

Null hypothesis (H₀)

There is no difference in the population means.
→ Uses = (or “no change” for paired tests)

how you would select the correct critical value to compare to

degrees of freedom and significance

how you would write a conclusion to a student t test if the result was significant 

The result is significant at the 0.05 level, so the null hypothesis is rejected. This means there is a statistically significant difference between the two means. The data therefore support the conclusion that [insert biological effect].

how you would write a conclusion to a student t test if the result was insignificant

The calculated t‑value was less than the critical value, so the result is not significant at the 0.05 level. The null hypothesis is retained. This means there is not enough evidence to conclude that the two means are different.

Give the definition of primary and secondary succession 

the gradual development of an ecosystem, changes the proportion of species over time

primary - development from nothing

secondary- rebuilding an ecosytem after damage

Give the definition of a pioneer species 

the first species to colonize an area

Explain how pioneer species are adapted to exploit their niche 

Generally extremeophiles, able to survive with very little nutrience in harrsh environmnets, break up the soil and decompose adding nutience

Explain how pioneer species change the abiotic conditions in an ecosystem 

they break up the soil and as they decompose they add nutrients to the soil

Give the definition of a climax community 

pioneer species are out competed until staability is reached, many species

Explain the stages of succession from colonisation to climax community

pioneer stage - pioneer species such as lichens and small plants

these decompose to add nutriients to the soil, and they break up the soil

SOIL IS FORMED

more plants and shrubs can grow who generally outcompete the pioneer species

CLIMAX COMMUNITY

eventually reaches a steady state where species are stable and few changes occur

balanced symbol equation for photosynthesis

the definition of photosynthesis 

Photosynthesis isthe process used by plants, algae, and some bacteria to turn sunlight, water, and carbon dioxide into oxygen and energy-making sugar

the meaning of the acronym OILRIG in relation to photosynthesis

oxidation Is Loss (of electrons), Reduction Is Gain (of electrons).
In photosynthesis, NADP is reduced when it gains electrons and H⁺ to form reduced NADP.

Give the equation to form ATP. State the name of the reaction and the enzyme responsible

:

Phosphorylation

Give the equation to breakdown ATP. State the name of the reaction and the enzyme responsible 

hydrolysis

Explain how ATP can be used as an energy source 

 ATP hydrolysed (ATP à ADP + Pi)

Phosphate hydrated/surrounded by water molecules

Energy released (when bonds formed between water and phosphate)

Describe the structure of ATP

a nitrogenous base, a pentose sugar, and a chain of three phosphate groups

Compare and contrast the structure of ATP to a DNA nucleotide

Both have a a pentose sugar phosphate and nitrogenous base

ATP= why both sugar Vs DNA = deoxyribose

ATP = always adenine DNA = Adenine thymine cytosine or guanine

State the site of light dependent reactions

thylakoid membrane

Describe photolysis

water broken down via light

State the term used to describe the production of ATP via the light dependent reaction. Explain why it is given this name 

photophosphorylation - splitting of water with light, adding phosphate group

State the term used to describe the process by which electrons move down the electron transport chain. Explain why the term is used 

redox reaction, both oxidation and reduction occur

State the three products of light dependent stage 

ATP, reduced NADP, O2

State the role of the three products of the light dependent stage 

ATP: Acts as a chemical energy carrier that transfers energy to power the light-independent reactions (Calvin cycle) in the stroma

Reduced NADP: Provides high-energy electrons and hydrogen ions needed to convert carbon compounds into sugars during the light-independent stage.

Oxygen: Released as a byproduct into the atmosphere (or used in cellular respiration) following the photolysis (splitting) of water molecules.

Describe the process of the light dependent stage

Takes place at thylakoid membrane/grana/granum

Light strikes chlorophyll, 2e^- released to a higher energy level

2e^- move down electron carrier molecules via redox reactions

ADP+Pi à ATP via ATP synthase

Water undergoes photolysis into 2e^- , 2H⁺ and ½ oxygen

2e^- replace those lost from chlorophyll

2H⁺ and 2e^- combine with NADP to form NADPH/reduced NADP

the site of the light independent reactions

stroma

the alternate name for the light independent reactions

calvin cycle

light independent reactions can be divided into three interlinked reactions

carbon fixation, reduction and phosphorylation

what happens in carbon fixation

RuBP +Co2 —> GP via RUBISCO

what happens in reduction

GP —>GALP

ATP—> ADP +Pi for energy

NADPH —> NADP for H+ ions and electrons

what happens in phosphorylation

GALP —>RuBP

using the phosphate form ATP —> ADP + Pi, it the inorganic phosphate

the process of the light independent stage

Occurs in the stroma

CARBON FIXATION

RuBP +Co2 —> GP via RUBISCO

REDUCTION

GP —>GALP

ATP—> ADP +Pi for energy

NADPH —> NADP for H+ ions and electrons

PHSOPHORYLATION

GALP —>RuBP

using the phosphate form ATP —> ADP + Pi, it the inorganic phosphate

2GALP —> 1 glucose

the products of the light independent stage can be used to produce cellulose cell walls

2x GALP - beta glucose, this can be polymerised to cellulose

the light independent stage relies on the light dependent stage occurring

It needs the products of ATP - for energy for GP —> GALP and phosphate to convert GALP to RuBP again

It also needs NADPH —> NADP for the hydrogen ions

Draw and label a diagram of the chloroplast, show on the diagram where the light dependent and light independent reactions occur 

LDR thylakoid membrane, LIR stroma

State the adaptations the chloroplast has for enabling photosynthesis

chlorophyll - light sensitive pigment which triggers the LDR

starch grain - holds energy

enzymes - cataluse the reactions

surface area - maximises the rate of the LDR and space that can hold excited H+ ions