IGCSE Biology Revision Unit 1-5

What 7 characteristics do all living organisms share?

• they move- they respire- they respond to their internal and external environment- they grow and develop- they reproduce- they excrete their waste- they require nutrition

Define movement

An action by an organism or part of an organism causing a change of position or place

Define respiration

The chemical reactions in cells that break down nutrient molecules and release energy for metabolism

Define sensitivity

The ability to detect and respond to changes in the internal or external environment

Define growth

A permanent increase in size and dry mass

Define reproduction

The processes that make more of the same kind of organism

Define excretion

The removal of the waste products of metabolism and substances in excess of requirements

Define nutrition

The taking in of materials for energy, growth and development

Why are viruses not living?

They do not have all of the 7 characteristics of living organisms (for example they cannot respire)

Define species

A group of organisms that can breed to produce fertile offspring

Give 2 ways that organisms can be classified

• Physical features- Evolutionary relationships

How are modern classification techniques more accurate? (Higher/Supplement)

Biochemical and genetic analysis gives a more precise and detailed understanding about the relationships of organisms

How can organisms that share recent common ancestors be identified? (Higher/Supplement)

• Analyse the organism's DNA- Organisms with more similar DNA sequences often share more common ancestors

What are the 5 kingdoms? (Higher/Supplement)

Animal, Plant, Fungus, Prokaryote, Protoctist

Describe the binomial naming system

The system used to name organisms using two names

Give 3 advantages of the binomial naming system

• It is universal- It provides information about closely linked organisms and hence their traits- It allows for precise naming

State the features that all cells share

Cytoplasm, cell membrane and DNA, ribosomes and enzymes for respiration

What are the two broad groups of animals?

Vertebrates and invertebrates

What is the difference between vertebrates and invertebrates?

Vertebrates have a backbone, invertebrates do not

What are the 5 main groups of vertebrates?

Mammals, birds, reptiles, amphibians, fish

What is an arthropod?

An invertebrate animal with an exoskeleton, segmented body, and jointed appendages

What are the 4 main groups of arthropods?

myriapods, insects, arachnids, crustaceans

What are the two broad groups of plants? (Higher/Supplement)

Flowering and non- flowering

What are the two main groups of flowering plants? (Higher/Supplement)

Monocotyledons and dicotyledons

What are dichotomous keys?

They are resources that are used to identify organisms by asking a series of contrasting questions

State 3 parts of an animal cell visible under a light microscope

Nucleus, cytoplasm, cell membrane

State 2 additional features of eukaryotic cells that are not visible under a light microscope

Mitochondria and ribosomes

What is the function of ribosomes?

Ribosomes are the site of protein synthesis

A very metabolically active cell is likely to have lots of which type of organelle?

Mitochondria as they produce energy through aerobic respiration

Label this animal cell

Label this plant cell

Label this light micrograph of an onion epidermal cell

State 6 parts of a plant cell visible under a light microscope

Nucleus, cytoplasm, chloroplasts, vacuoles, cell wall and the cell membrane

State the organelles that a bacterial cell contains

Cell wall, cell membrane, cytoplasm, circular DNA, plasmids and ribosomes

State 2 functions of the nucleus

• Controls the cell- Contains genetic material - found in the form of chromosomes

State the function of the cytoplasm

It is where most of the cell's chemical reactions take place

State 3 organelles only found in plant cells

• Cellulose cell wall- Permanent vacuole- Chloroplasts

What is the function of the cell wall and what is it made of?

It provides strength and support. It is made of cellulose (in plants).

What is the function of the permanent vacuole and what does it contain?

It supports the cell and contains cell sap (a solution of sugars and salts)

What is the function of chloroplasts?

They are the site of photosynthesis

State 2 organelles only found in bacterial cells

Plasmids and circular DNA

What is the function of plasmids?

Contain extra genes in addition to those in the circular DNA

What is the function of ciliated epithelial cells?

They waft away mucus, dirt and debris up the throat where it can be swallowed

How are ciliated epithelial cells adapted to their function?

• Small cilia that line the exposed surface can waft back and forwards- The cilia are long and thin so that lots of them can waft at the same time

What is the function of root hair cells?

To take up minerals and water needed by the plant

How are root hair cells adapted to their function?

• They have lots of mitochondria to provide energy for active transport- They have a long extension to maximise the surface area available for uptake

What is the function of palisade mesophyll cells?

Their main function is to absorb light and carry out photosynthesis

How are palisade mesophyll cells adapted to their function?

• Contain lots of chloroplasts to carry out photosynthesis- Thin and tall so that many can be packed together- Large vacuole pushes chloroplasts to the outside of the cell- Thin cell wall to minimise the diffusion distance

What is the function of red blood cells?

Red blood cells carry oxygen from the lungs to tissues and carbon dioxide from tissues to the lungs to be exhaled

How are red blood cells adapted to their function?

• No nucleus so there is more room for haemoglobin- Contain lots of haemoglobin to carry oxygen- Biconcave shape giving a large surface area to volume ratio- Thin membrane to minimise the diffusion distance for gases

What is the function of neurones?

To transmit electrical impulses around the body

How are neurones adapted to their function?

They are long and have branched endings to connect to other neurones

What is the function of a sperm cell?

To travel to, penetrate and fertilise an egg cell

How are sperm cells adapted to their function?

• They contain a long tail to help it swim to the egg- They have a middle section containing lots of mitochondria which provide the cell with energy for swimming to the egg- They have an acrosome at the tip containing enzymes to digest the outer membrane of the egg

What is the function of an egg cell?

To fuse with a sperm cell for reproduction

How is an egg cell adapted to its function?

• Haploid nucleus so that after fusing with a sperm it produces a diploid organism- Lots of cytoplasm for many divisions- Lots of nutrients to support the egg until it reaches the womb

Define cell

Basic building block of all living organisms

Define tissue

A group of similar cells working together to perform a specific function

Define organ

A group of different tissues working together to perform a specific function

Define organ system

A group of organs working together to carry out a specific function

Name 3 organ systems in the body

Circulatory system, digestive system, respiratory system

What tissues make up a plant leaf?

Epidermal tissue, mesophyll tissue, vascular tissue

What organs make up the circulatory system?

• The heart- The lungs- The blood vessels

What type of tissue is the heart made up of?

Cardiac muscle

What organs make up the digestive system?

The oesophagus, stomach, small intestine, large intestine, liver, pancreas, gallbladder and anus

Is this diagram an example of a tissue, organ or organ system?

This is an organ system (the respiratory system) which is made of multiple different organs working together

Is this diagram an example of a tissue, organ or organ system?

This is an organ (the heart) which is made of multiple different tissues

Is this diagram an example of a tissue, organ or organ system?

This is an organ (the brain) which is made of multiple different tissues

Is this diagram an example of a tissue, organ or organ system?

This is an organ system (the digestive system) which is made of multiple different organs working together

Define magnification

How much larger a displayed image is compared with the original object

What is the formula to calculate magnification from image size and actual size?

Magnification = image size / actual size

If a cell with an actual size of 0.05mm in diameter is viewed under a microscope with a 200x power lens, what will the size of the image be in mm?

Image size = actual size x magnification = 0.05 x 200 = 10mm

If an image of a cell is 50mm in diameter when viewed under a 800x microscope, what is the size of the actual cell in mm?

Image size = 50mm, Magnification = 800x, I = A x M can be rearranged to I / M = A, 50/800 = 0.0625mm

How do you convert from mm to cm?

Divide by 10, E.g. 100 mm = 10 cm

How do you convert from cm to mm?

Multiply by 10, E.g. 5 cm = 50 mm

How do you convert from mm to μm? (Higher/Supplement)

Multiply by 1000, E.g. 50mm = 50,000μm

How do you convert from μm to mm? (Higher/Supplement)

Divide by 1000, E.g. 6μm = 0.006mm

Define diffusion

The net movement of molecules from an area of high concentration to an area of low concentration down their concentration gradient

Where does the energy for the movement of particles in diffusion come from?

From the kinetic energy of the particles that causes them to move in random directions

Why is the diffusion of gases important?

It allows for gas exchange in organisms to provide useful gases for processes like respiration and to remove waste gases

Why is the diffusion of solutes important?

It is useful for the uptake of solutes from the soil in plants

How does temperature affect the rate of diffusion?

As the temperature increases, so does the rate of diffusion as the particles have more kinetic energy and move faster

How does the concentration gradient affect the rate of diffusion?

The greater the concentration gradient (the difference between the two areas), the faster the rate of diffusion

How does the surface area of the membrane affect the rate of diffusion?

As the surface area increases so does the rate of diffusion as there is more space for the particles to move through

How does the diffusion distance affect the diffusion rate?

The shorter the diffusion distance, the faster the rate of diffusion

Give one use of water in the body

Water is used as a solvent in the body

Give 3 processes in which water is used as a solvent

Digestion, excretion, transport

What is osmosis?

The passive diffusion of water through a partially permeable membrane

Define osmosis (Higher/Supplement)

The net movement of water molecules from a high water potential to a low water potential across a partially permeable membrane

What is a hypotonic solution? (Higher/Supplement)

A solution that has a higher water potential than the water potential of the cell

What happens if you place an animal cell in a hypotonic solution? (Higher/Supplement)

There is a net movement of water into the cell which causes the animal cell to burst (lysis)

What happens if you place a plant cell in a hypotonic solution? (Higher/Supplement)

There is a net movement of water into the cell which causes the plant cell to become turgid (it does not burst because of the strong cell wall)

What is a hypertonic solution? (Higher/Supplement)

A solution that has a lower water potential than the water potential of the cell

What happens if you place an animal cell in a hypertonic solution? (Higher/Supplement)

There is a net movement of water out of the cell which causes the animal cell to shrink (crenate)

What happens if you place a plant cell in a hypertonic solution? (Higher/Supplement)

There is a net movement of water out of the cell which causes the plant cell to become plasmolysed (the cell membrane peels away from the cell wall)

How is a plant cell supported?

Water within the vacuole creates pressure which supports the cell. The cell wall also provides support.

Explain how the water in cells supports them (Higher/Supplement)

The water creates turgor pressure which pushes the cell membrane against the inelastic cell wall

Define active transport

The movement of molecules from a low concentration to a high concentration against their concentration gradient using energy from respiration

Give one use of active transport in humans (Higher/Supplement)

• Uptake of minerals and nutrients in the small intestine- Reabsorption in the kidney

Give one use of active transport in plants (Higher/Supplement)

Uptake of minerals into root hair cells