1. Gas exchange in humans, cell structure, and organisms.

What is the function of gas exchange surfaces?

They allow oxygen to diffuse into the blood and carbon dioxide to diffuse out.

What features do all gas exchange surfaces share?

Large surface area thin walls good ventilation and good blood supply.

Why is a large surface area important for gas exchange?

It allows more gas to diffuse at the same time increasing the rate of diffusion.

Why must gas exchange surfaces be thin?

Thin walls reduce diffusion distance making diffusion faster.

Why is a good blood supply important in gas exchange surfaces?

It maintains a steep concentration gradient for diffusion.

What is the gas exchange surface in humans?

The alveoli.

What type of wave is breathing controlled by?

Muscle contraction controlled by the nervous system.

What structures make up the human breathing system?

Trachea bronchi bronchioles alveoli lungs diaphragm and intercostal muscles.

What is the role of the trachea?

It carries air to and from the lungs.

Why does the trachea have rings of cartilage?

To prevent it collapsing during breathing.

What happens during inhalation?

Diaphragm contracts ribs move up and out volume increases pressure decreases air enters lungs.

What happens during exhalation?

Diaphragm relaxes ribs move down and in volume decreases pressure increases air leaves lungs.

What is the function of external intercostal muscles?

They lift the rib cage up and out during inhalation.

What is the function of internal intercostal muscles?

They pull the rib cage down and in during forced exhalation.

What test is used to detect carbon dioxide?

The limewater test.

What happens to limewater in the presence of carbon dioxide?

It turns cloudy or milky.

Why does expired air contain more carbon dioxide?

Carbon dioxide diffuses from the blood into the alveoli during gas exchange.

What percentage of oxygen is in inspired air?

About 21 percent.

What percentage of oxygen is in expired air?

About 16 percent.

Why does expired air contain less oxygen?

Oxygen diffuses into the blood for respiration.

Why does expired air contain more water vapour?

Water evaporates from moist alveoli surfaces.

How does exercise affect breathing rate?

Breathing rate and depth increase.

Why consider breathing rate after exercise?

To repay oxygen debt and remove carbon dioxide.

What is oxygen debt?

Extra oxygen needed to break down lactic acid after anaerobic respiration.

What causes lactic acid production?

Anaerobic respiration when oxygen is insufficient.

How does carbon dioxide affect breathing rate?

High carbon dioxide lowers blood pH triggering increased breathing.

Where are chemoreceptors located?

In the medulla oblongata of the brain.

What is the role of cilia in the airways?

They move mucus away from the lungs.

What do goblet cells produce?

Mucus.

Why is mucus important?

It traps dust bacteria and pathogens.

What structure contains DNA?

Nucleus

What is the function of the cytoplasm?

Site of chemical reactions and supports organelles

What is the function of the cell membrane?

Controls entry and exit of substances

What is the function of ribosomes?

Protein synthesis

What is the function of mitochondria?

Site of aerobic respiration

What extra structure do plant cells have that animals do not?

Cell wall

What is the function of the cell wall?

Provides support and maintains shape

What are chloroplasts used for?

Photosynthesis

What pigment is found in chloroplasts?

Chlorophyll

What does the permanent vacuole contain?

Cell sap

What is the function of the vacuole?

Storage and maintaining turgor

What type of cells are bacteria?

Prokaryotic

Do bacteria have a nucleus?

No

What genetic material do bacteria have?

Circular DNA

What are plasmids?

Small rings of DNA carrying extra genes

Do bacteria have mitochondria?

No

What is a flagellum?

A structure used for movement in some bacteria

What is differentiation?

Process where cells become specialised

Give an example of a specialised animal cell

Nerve cell

How is a red blood cell adapted to its function?

Biconcave shape and no nucleus for oxygen transport

What is the function of ciliated cells?

Move mucus in the airways

What is the function of root hair cells?

Absorb water and mineral ions

What is the function of xylem cells?

Transport water and provide support

What is the order of organisation?

Cell → Tissue → Organ → Organ system → Organism

What is magnification?

How many times larger an image is compared to real size

State the magnification formula

Magnification = image size ÷ actual size

Does magnification have units?

No

What unit is often used for cells?

Micrometres (µm)

How many micrometres are in 1 mm?

1000 µm

Why must units be the same in calculations?

To avoid incorrect magnification values

What are the seven characteristics of life?

Movement Respiration Sensitivity Growth Reproduction Excretion Nutrition

What does respiration mean?

Chemical reactions releasing energy in cells

What does excretion mean?

Removal of toxic waste and excess substances

What is a species?

A group of organisms that can reproduce to produce fertile offspring

What is binomial naming?

Naming organisms using genus and species

Which part of the binomial name is capitalised?

Genus

Which part of the binomial name is lowercase?

Species

What language is binomial naming written in?

Latin

What is the classification order?

Kingdom Phylum Class Order Family Genus Species

What is a dichotomous key?

A tool used to identify organisms using paired statements

What does dichotomous mean?

Branching into two

Why are DNA sequences useful in classification?

They show evolutionary relationships

What does similar DNA indicate?

A close evolutionary relationship

Name the five kingdoms

Animals Plants Fungi Protoctists Prokaryotes

What are main features of animals?

Multicellular no cell walls heterotrophic

What are main features of plants?

Multicellular cellulose walls chloroplasts photosynthesis

What are fungi?

Organisms that feed saprophytically or parasitically

Are fungi photosynthetic?

No

What are protoctists?

Mostly unicellular organisms with a nucleus

What are prokaryotes?

Unicellular organisms with no nucleus

What defines vertebrates?

Presence of a backbone

What defines invertebrates?

No backbone

What phylum do insects belong to?

Arthropods

What is a defining feature of arthropods?

Jointed legs

What feature defines mammals?

Fur and mammary glands

How do monocots differ from dicots in petals?

Monocots in 3s dicots in 4s or 5s

How do monocots differ from dicots in leaves?

Parallel veins vs reticulated veins

How do ferns reproduce?

By spores

How do flowering plants reproduce?

By flowers and seeds

Are viruses living?

No

Why are viruses not classified as living?

They do not carry out life processes independently

What is a virus made of?

Genetic material inside a protein coat