Adaptations for Gas Exchange (AQA A Level Biology): Flashcards

True.

Surface area to volume ratios are typically written in the form x:1, where x is the surface area divided by the volume.

The surface area of a cube is calculated as 6a² and the volume as a³.

The surface area to volume ratio is the proportion of the surface area of an object compared to its volume.

The surface area to volume ratio is a comparison of the amount of surface area of an object to its volume. It determines how much surface is available for diffusion relative to the amount of material inside.

The diffusion rate is the speed at which particles move from an area of higher concentration to an area of lower concentration.

Agar blocks containing indicator are used to visually track how far or how fast diffusion occurs by showing a colour change as diffusion happens.

The two factors that can be investigated are the surface area to volume ratio and the concentration gradient.

A higher surface area to volume ratio increases the rate of diffusion in agar cubes.

False.

Agar cubes with a higher surface area to volume ratio show a faster colour change because more surface is available for diffusion relative to the volume.

To calculate the surface area to volume ratio of a cube, use the formula: surface area divided by volume.

Diffusion rate can be measured by recording the time taken for the agar cubes to entirely change colour or the distance the colour change travels into the block in a given time.

Agar cubes are placed in dilute hydrochloric acid so the colour change is due to a change in pH.

Using the same volume and concentration of acid ensures a fair test by making sure only the variable being investigated (such as surface area to volume ratio) affects the diffusion rate.

The surface area to volume ratio (SA:V ratio) is the proportion of the total external surface area of an organism compared to its volume.

Single-celled organisms have a high surface area to volume ratio, so diffusion across the cell surface is enough to meet the needs of the cell.

As organisms increase in size, their surface area to volume ratio decreases.

False.

Although larger organisms have a greater total surface area, their surface area to volume ratio is smaller than that of smaller organisms.

Adaptations for exchange are specialised structures or features that allow large organisms to efficiently exchange substances with their environment.

Large multicellular organisms have adaptations to help them exchange substances with their environment.

The small volume of a single-celled organism means the diffusion distance to all parts of the cell is short.

In a single-celled organism, the large surface area allows for the maximum diffusion of nutrients and gases.

As an organism increases in size, its greater volume results in a longer diffusion distance to all parts of the organism.

For example, there may be many layers of cells for substances to pass through.

In mammals, the gas exchange system and the digestive system.

In plants, the leaves.

True.

Leaves have a large internal surface area, an adaptation that facilitates gas exchange by diffusion in plants.

Large organisms have a low surface area to volume ratio, so simple diffusion across the body surface alone cannot meet their needs.

Specialised exchange surfaces facilitate the exchange of substances with the environment.

The surface area to volume ratio is the proportion of an organism’s external surface area compared to its total volume. It affects how quickly substances like heat and gases are exchanged with the environment.

An organism’s surface area to volume ratio is related to its metabolic rate because a higher ratio leads to greater heat loss, requiring a higher metabolic rate to maintain body temperature.

The metabolic rate of an organism is the energy expended by that organism within a given period of time.

False.

Small animals lose more heat to their surroundings because they have a higher surface area to volume ratio.

Large animals, with a lower surface area to volume ratio, lose less heat and have a relatively low metabolic rate.

Small animals have a higher surface area to volume ratio, so they lose heat more rapidly and must have a higher metabolic rate to maintain their body temperature.

Heat is lost to the environment at the body's surface.

A large surface area in relation to volume therefore allows more heat to be lost.

True.

Small animals have a smaller total surface area than large animals, but a higher surface area to volume ratio.

An elephant has a greater total BMR than a mouse.

However, the elephant has a lower BMR per unit mass than the mouse.

A high surface area to volume ratio means there is a large surface in relation to volume.

This causes more heat to be lost to the environment.

A high metabolic rate is needed to replace this heat and maintain body temperature.

Basal metabolic rate per unit mass decreases as the mass of an animal increases.

A gas exchange surface is a specialised area that enables efficient movement of respiratory gases, such as oxygen and carbon dioxide, between an organism and its environment.

Effective gas exchange surfaces must have a large surface area, a short diffusion distance, and a steep concentration gradient.

The two main gases exchanged during respiration are oxygen (supplied for respiration) and carbon dioxide (removed as a waste product).

Diffusion is the passive movement of molecules from a region of high concentration to a region of low concentration.

A high surface area to volume ratio allows single-celled organisms to efficiently exchange gases by diffusion across their entire cell surface, ensuring all parts of the cell receive oxygen and remove carbon dioxide quickly.

In single-celled organisms like amoeba, the diffusion distance from the surface to all parts of the cell is short.

False.

Insects use a tracheal system for gas exchange, not lungs.

Air enters an insect’s body through openings called spiracles, which lead to tubes known as tracheae.

The counter-current system in fish gills ensures that blood flows in the opposite direction to water, maintaining a steep concentration gradient for gas exchange along the entire length of the gill.

Each gill filament in fish is covered with rows of lamellae, which have a single layer of flattened cells and a rich supply of capillaries.

Stomata are pores on the underside of leaves that allow gases such as carbon dioxide and oxygen to diffuse in and out of the leaf for photosynthesis and respiration.

The spongy mesophyll layer and the presence of air spaces in plant leaves help to provide a large surface area for gas exchange.

Leaves are flat and thin to reduce the diffusion distance for gases, making gas exchange more efficient.

A xerophytic plant is a plant adapted to live in dry environments by reducing water loss through specialised features such as a thick waxy cuticle, few stomata, or leaves reduced to spines.

Adaptations that aid gas exchange often increase water loss because they require openings or surfaces that allow gases and water vapour to move freely, making it easier for water to evaporate.

Terrestrial insects minimise water loss by having a waterproof exoskeleton and the ability to close their spiracles.

Hairs around insect spiracles reduce the diffusion of water vapour, helping to minimise water loss.

Xerophytic plants often have stomata located in pits or surrounded by hairs.

Needle-shaped leaves reduce the surface area available for water loss through evaporation, helping xerophytic plants conserve water.

A waxy cuticle is a waterproof layer covering the epidermis of plant leaves and stems, reducing water loss by evaporation.

Cacti have leaves reduced to spines and a stem with a thick cuticle to prevent water loss.

True.

Marram grass can roll its leaves to create grooves that protect stomata, reducing water loss from wind exposure.

A spiracle is a small opening on the surface of an insect's body that allows for gas exchange but can also be a site of water loss.