Life processes and unicellular organisms

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Life Processes (MRS GREN)

All living organisms perform **seven life processes**, remembered by the acronym **MRS GREN**.
**Movement**: All living things move; plants grow towards light, animals move to find food or escape danger.
**Respiration**: A chemical reaction that **releases energy** stored in glucose.
**Sensitivity**: Living things **sense changes** in their environment and respond (e.g., humans feel heat, plants grow towards light).
**Growth**: Organisms increase in size; unicellular organisms grow by increasing cell size, multicellular by producing more cells.
**Reproduction**: The process of **producing offspring**.
**Excretion**: The **removal of waste products** from the body.
**Nutrition**: Plants photosynthesise; animals eat plants or other animals.

Unicellular Organisms

**Unicellular organisms** are living organisms made of **just one cell**.
Despite their small size, they perform **all seven life processes**.
Examples include **bacteria**, **euglena**, **amoebas**, and **yeast** (a fungus).

Bacteria

Bacteria are some of the most common and diverse unicellular organisms.
They **do not have a nucleus**; genetic material is located in the **nucleoid** and **plasmids**.
Some bacteria have a long tail called a **flagellum** for movement.
Bacteria have a **cell wall**, **cell membrane**, and **ribosomes**.

Euglena

Euglena is a unicellular organism found in water.
It has a **flagellum** to help it swim.
It contains **chloroplasts** for photosynthesis.
It also has an **eyespot** for light sensitivity (not mentioned in source, but typical; source only mentions flagellum and chloroplasts).

Other Unicellular Organisms

**Amoebas** are unicellular organisms that move and feed using pseudopods.
**Yeast** is a unicellular fungus used in baking and brewing.

Structure of a bacterium, a unicellular prokaryote.

Euglena, a unicellular organism with a flagellum and chloroplasts.

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Practice questions

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1.How many life processes do all living organisms perform?
Easy
- ASeven
- BFive
- CSix
- DEight
2.What does the acronym MRS GREN help us remember?
Easy
- AThe life processes of living organisms
- BThe parts of a bacterium
- CThe organelles of a euglena
- DThe types of unicellular organisms
3.Which of the following is NOT a life process?
Easy
- APhotosynthesis
- BRespiration
- CExcretion
- DSensitivity
4.Which statement about unicellular organisms is correct?
Easy
- AThey are made of one cell and perform all life processes.
- BThey are made of many cells and perform only some life processes.
- CThey are made of one cell and perform only some life processes.
- DThey are made of many cells and perform all life processes.
5.Which of the following is an example of a unicellular organism?
Easy
- ABacterium
- BHuman
- COak tree
- DMushroom
6.Bacteria do not have a nucleus. Where is their genetic material located?
Medium
- AIn the nucleoid and plasmids
- BIn the nucleus
- CIn the cytoplasm
- DIn the cell wall
7.What is the function of the flagellum in some bacteria?
Medium
- AMovement
- BRespiration
- CReproduction
- DNutrition
8.Which process is defined as 'a chemical reaction that releases energy stored in glucose'?
Medium
- ARespiration
- BPhotosynthesis
- CExcretion
- DNutrition

More questions

9.Euglena is a unicellular organism that can photosynthesise. Which organelle allows it to do this?
Medium
- AChloroplast
- BMitochondrion
- CNucleus
- DFlagellum
10.Which of the following is NOT a life process according to MRS GREN?
Hard
- ADigestion
- BMovement
- CGrowth
- DReproduction
11.Which of the following statements about bacteria is true?
Hard
- ASome bacteria have a flagellum for movement.
- BAll bacteria have a nucleus.
- CBacteria are multicellular organisms.
- DBacteria do not contain genetic material.
12.A student observes a unicellular organism under a microscope. It has a flagellum and chloroplasts. Which organism is it most likely to be?
Hard
- AEuglena
- BAmoeba
- CYeast
- DBacterium
13.A student investigates the effect of temperature on the growth of yeast. The results are shown in the table. At which temperature did yeast grow the most?
Medium
- A15°C
- B25°C
- C35°C
- D45°C
14.A culture of bacteria is placed in a solution with a high concentration of antibiotic. After 24 hours, the number of living bacteria is counted. Which graph shows the expected change in the number of living bacteria over time?
Hard
- AA line decreasing steadily to zero
- BA line increasing steadily
- CA line that falls sharply then levels off
- DA line that remains constant
15.A unicellular organism lives in a pond. It has no chloroplasts and feeds on other microorganisms. Which life process does this organism carry out to obtain food?
Medium
- APhotosynthesis
- BRespiration
- CNutrition
- DExcretion
16.Which of the following is a waste product that must be excreted by unicellular organisms?
Easy
- AGlucose
- BOxygen
- CCarbon dioxide
- DWater
17.A student measures the rate of respiration in yeast at different temperatures. The results are shown in the bar chart. Which temperature gives the highest rate of respiration?
Hard
- A10°C
- B20°C
- C30°C
- D40°C
18.A biologist observes a unicellular organism under a microscope. It moves by extending its cell membrane and flowing forward. Which organism is it most likely to be?
Medium
- AEuglena
- BAmoeba
- CYeast
- DBacterium
19.Which of the following life processes is most directly involved when a unicellular organism moves towards a light source?
Medium
- AMovement
- BSensitivity
- CGrowth
- DRespiration
20.All living organisms carry out respiration. What is the main purpose of respiration?
Easy
- ATo produce glucose
- BTo release energy
- CTo remove waste
- DTo move
21.A scientist cultures two species of bacteria: one with a flagellum and one without. Both are placed in a liquid medium with nutrients. After 24 hours, the species with a flagellum is found in higher numbers. Which life process does the flagellum help with?
Hard
- ANutrition
- BMovement
- CReproduction
- DExcretion
22.A student observes a unicellular organism under a microscope. It has no nucleus but has a flagellum. Which organism is it most likely to be?
Medium
- AA bacterium
- BA euglena
- CAn amoeba
- DA yeast
23.A scientist cultures two species of bacteria: one with a flagellum and one without. Both are placed in a liquid medium with nutrients. After 24 hours, the species with a flagellum has spread throughout the container, while the other remains near the initial spot. This observation best demonstrates which life process?
Medium
- AGrowth
- BMovement
- CReproduction
- DNutrition
24.A student sets up an experiment to measure the rate of respiration in yeast at different temperatures. Which piece of equipment would be most suitable to measure the rate of respiration?
Hard
- AA thermometer
- BA pH meter
- CA gas syringe
- DA balance
25.Which of the following statements about bacteria is correct?
Medium
- ABacteria have a nucleus containing their genetic material.
- BBacteria are multicellular organisms.
- CBacteria have genetic material in a nucleoid and plasmids.
- DBacteria do not carry out respiration.
26.A student uses a microscope to observe a sample of pond water. She sees a unicellular organism that contains chloroplasts and a flagellum. Which life process is this organism able to carry out that a bacterium without chloroplasts cannot?
Hard
- AMovement
- BRespiration
- CPhotosynthesis
- DExcretion
27.In an experiment, a student adds a drop of pond water containing euglena to a dish with a light source at one end. After 10 minutes, most euglena are near the light. This response is an example of which life process?
Medium
- AMovement
- BSensitivity
- CNutrition
- DReproduction
28.A student observes a unicellular organism from pond water. It has a flagellum and can photosynthesise. Which organism is it most likely to be?
Medium
- AEuglena
- BAmoeba
- CYeast
- DBacterium
29.In an experiment, a student adds a drop of pond water containing euglena to a dish with a light source at one end. After 10 minutes, most euglena are near the light. Which life process does this behaviour illustrate?
Medium
- ASensitivity
- BMovement
- CNutrition
- DReproduction
30.A scientist cultures two species of bacteria: one with a flagellum and one without. Both are placed in a liquid medium with nutrients. After 24 hours, the species with a flagellum has a larger population. Which is the most likely explanation?
Hard
- AThe flagellum allows the bacteria to move towards nutrients more effectively.
- BThe flagellum helps the bacteria to reproduce faster.
- CThe flagellum enables the bacteria to photosynthesise.
- DThe flagellum helps the bacteria to excrete waste.
31.A student measures the rate of respiration in yeast at different temperatures. The results are shown in the bar chart. Which temperature gives the highest rate of respiration? (Assume the bar chart shows: 10°C: 2 bubbles/min, 20°C: 4 bubbles/min, 30°C: 6 bubbles/min, 40°C: 5 bubbles/min)
Hard
- A30°C
- B20°C
- C40°C
- D10°C
32.A student sets up an experiment to measure the rate of respiration in yeast at different temperatures. Which piece of equipment would be most suitable to measure the volume of carbon dioxide produced?
Hard
- AA gas syringe
- BA thermometer
- CA balance
- DA ruler
33.A student uses a microscope to observe a sample of pond water. She sees a unicellular organism that contains chloroplasts and a flagellum. Which life process is the flagellum primarily used for?
Medium
- AMovement
- BNutrition
- CRespiration
- DExcretion
34.A student investigates the effect of temperature on the growth of yeast. The results are shown in the table. At which temperature did yeast grow the most? (Table: 15°C: 2 colonies, 25°C: 5 colonies, 35°C: 8 colonies, 45°C: 3 colonies)
Hard
- A35°C
- B25°C
- C45°C
- D15°C
35.A culture of bacteria is placed in a solution with a high concentration of antibiotic. After 24 hours, the number of living bacteria is counted. Which graph shows the expected change in the number of living bacteria over time? (Assume the correct graph shows a rapid decrease then plateau; distractors show increase, no change, or gradual increase)
Medium
- AA rapid decrease then plateau
- BA steady increase
- CNo change
- DA gradual increase then decrease
36.A student observes a unicellular organism from pond water under a microscope. It has a flagellum and chloroplasts. Which organism is it most likely to be?
Medium
- AEuglena
- BAmoeba
- CYeast
- DBacterium
37.A student sets up an experiment to investigate the effect of temperature on the growth of yeast. They prepare five test tubes with the same volume of sugar solution and add the same mass of yeast to each. The tubes are placed at different temperatures for 24 hours. Which of the following should the student measure to determine the amount of growth?
Medium
- AThe number of yeast cells using a microscope and haemocytometer
- BThe volume of gas produced using a gas syringe
- CThe change in pH using a pH meter
- DThe colour change using a colorimeter
38.A scientist cultures two species of bacteria: one with a flagellum and one without. Both are placed in a liquid medium with nutrients. After 24 hours, the species with the flagellum is found in higher numbers throughout the medium, while the other species is concentrated at the bottom. Which life process best explains this difference?
Hard
- AMovement
- BRespiration
- CNutrition
- DReproduction
39.A student uses a microscope to observe a sample of pond water. She sees a unicellular organism that contains chloroplasts and a flagellum. Which life process is this organism carrying out when it uses its flagellum to swim towards light?
Medium
- ASensitivity
- BMovement
- CNutrition
- DRespiration
40.In an experiment, a student adds a drop of pond water containing euglena to a dish with a light source at one end. After 10 minutes, most euglena are near the light. Which two life processes are demonstrated by this behaviour?
Hard
- ASensitivity and movement
- BNutrition and growth
- CRespiration and excretion
- DReproduction and nutrition

Revision notes

## Life Processes and Unicellular Organisms All living organisms carry out **seven life processes**, remembered by the acronym **Mrs. Gren**: - **M**ovement: All living things move (e.g., plants grow towards light, animals move to find food). - **R**espiration: A chemical reaction that releases energy stored in glucose. - **S**ensitivity: Sensing changes in the environment and responding (e.g., humans feel heat, plants grow towards light). - **G**rowth: Increase in size (unicellular) or number of cells (multicellular). - **R**eproduction: Producing offspring. - **E**xcretion: Removing waste products from the body. - **N**utrition: Plants photosynthesise; animals eat plants or other animals. **Unicellular organisms** are living organisms made of just one cell. They perform all seven life processes. Examples include: - **Bacteria**: No nucleus; genetic material in nucleoid and plasmids. Some have a flagellum for movement. - **Euglena**: Found in water; has a flagellum for swimming and chloroplasts for photosynthesis. - **Amoeba** and **yeast** (a fungus). Key points: - Bacteria do **not** have a nucleus. - Euglena have chloroplasts (photosynthesis) and a flagellum (movement). - Not all living things carry out photosynthesis (only plants and some unicellular organisms like euglena).

Unicellular organism: A living organism made of just one cell.
Mrs. Gren: Acronym for the seven life processes: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.
Respiration: A chemical reaction that releases energy stored in glucose.
Flagellum: A long tail used for movement in some unicellular organisms (e.g., bacteria, euglena).
Nucleoid: Region in bacteria where genetic material is located (no nucleus).
Plasmid: Small circular DNA in bacteria, separate from the nucleoid.
Chloroplast: Organelle in euglena (and plants) that carries out photosynthesis.

Flashcards

What does the acronym MRS GREN stand for?

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.

What is a unicellular organism?

A living organism made of just one cell.

How many life processes do all living organisms perform?

Seven.

Define movement in the context of life processes.

All living organisms move in some way; plants move slowly towards light, animals move to find food or escape danger.

What is respiration?

A chemical reaction that releases energy stored in glucose.

Define sensitivity.

Living things can sense changes in their environment and respond to them.

How do unicellular organisms grow?

They grow by increasing in size.

What is reproduction?

The process of producing offspring.

Define excretion.

The process of removing waste products from the body.

How do animals obtain nutrition?

Animals need to eat plants or other animals.

How do plants obtain nutrition?

Plants photosynthesise.

Do bacteria have a nucleus?

No, bacteria do not have a nucleus.

Where is genetic material located in bacteria?

In the nucleoid and plasmids.

What is a flagellum?

A long tail used for movement, found in some bacteria and euglena.

Name three examples of unicellular organisms.

Bacteria, euglena, amoebas, and some fungi such as yeast.

What organelles does euglena have for movement and photosynthesis?

A flagellum for swimming and chloroplasts for photosynthesis.

True or false: All living organisms carry out respiration.

True.

True or false: All living organisms carry out photosynthesis.

False.

True or false: Unicellular organisms are made of more than one cell.

False.

True or false: Bacteria contain a nucleus.

False.

What is the purpose of the flagellum in bacteria?

Movement.

What is the purpose of chloroplasts in euglena?

Photosynthesis.

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