Adaptions/Specializations

Unit 1 Biology

Ciliated cells

Function:

movement of mucus in

the trachea and bronchi

Structural adaptations:

Hair like projections called cilia which are

motile

Neurons

Function:

conduction of electrical

impulses

Structural adaptions:

Very long cells with projections /

branches called the axon and the

dendrites – for faster transmission of

impulses.

Most neurons are covered by a myelin

sheath which prevents the leakage of

impulses.

Red Blood Cells

Function:

transport of oxygen

Structural adaptions: 

Biconcave disc shape which allows for

greater surface area for the absorption of

oxygen.

No nucleus – more space for haemoglobin

which binds with oxygen to transport it.

Sperm Cells

Function:

reproduction

Structural Adaptions:

Flagellum / tail and streamline shape – for

movement towards the egg.

Multiple mitochondria – energy for

movement.

Root Hair Cell

Function:

Absorption of water and

mineral ions

Structural Adaptions: 

Cytoplasmic projection – increases the

surface area for absorption

Multiple mitochondria for active transport

of mineral ions.

Epidermal cells

Guard cells

Root hair cells

Root epidermis cells

Xylem vessels

Sieve tube cells /

elements

Companion cells

Palisade cells

Spongy mesophyll cells

Leaf Epidermis 

Epidermal cells:

• thin and transparent to allow light to pass through for photosynthesis.

• Some secrete a waxy cuticle to reduce water loss.

Guard cells

• They can change shape to open or close the stomata.

• When the plant has plenty of water, guard cells take in water, become turgid, and the stomata open for gas exchange.

• When water is scarce, they become flaccid and the stomata close to reduce water loss.

Root epidermis tissue

Root hair cells: 

• Have long, thin extensions (root hairs) to give a large surface area for absorbing water and mineral ions from the soil.

• Have a thin cell wall for a short diffusion distance.

• Contain many mitochondria to provide energy for active transport of minerals.

Root epidermis cells:

• Protect the root and absorb water and minerals from the soil.

• Some of them become root hair cells, increasing the surface area for absorption.

Xylem 

Xylem vessels: 

• Carry water and mineral ions from the roots to the rest of the plant.

• Made of dead cells joined end to end to form long, hollow tubes.

• Have no end walls, so water can flow easily.

Phloem 

Sieve tube: 

• Joined end to end to form long tubes for transport.

• Sieve plates in end walls allow movement of sugars between cells.

• Very little cytoplasm and no nucleus – provides more space for translocation of sugars.

Companion cells: 

• Have many mitochondria to supply energy (ATP) for active transport of sugars.

• Nucleus and cytoplasm help control and support sieve tube elements.

• Connected to sieve tube elements by plasmodesmata (tiny pores) for easy transfer of substances.

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Mesophyll tissue

Palisade cells – adaptations

• Contain many chloroplasts for photosynthesis.

• Tall and tightly packed to absorb lots of light.

• Thin cell walls to allow carbon dioxide to diffuse in easily.

Spongy mesophyll cells – adaptations

• Have air spaces between cells to allow easy gas exchange (carbon dioxide in, oxygen out).

• Have some chloroplasts for photosynthesis, though fewer than palisade cells.

• Thin cell walls to make gas diffusion faster.

How the small intestines are adapted to exchange materials in mammals 

Adaptations:

1. Long length – gives a large surface area and enough time for absorption of nutrients.

2. Folds, villi, and microvilli –

   • The inner surface is folded and covered with many villi (small finger-like projections).

   • Each villus has microvilli on its epithelial cells. increases the surface area for absorption.

3. Thin walls 

   • Short diffusion distance, so nutrients like glucose and amino acids can quickly pass into the blood.

4. Rich blood supply –

   • Each villus has a network of capillaries, which quickly carry absorbed nutrients away, keeping a steep concentration gradient for diffusion and active transport.

Moist surface –

• Allows nutrients to dissolve before diffusing through the epithelial cells.

How the lungs are adapted to exchange materials in mammals 

• Large surface area –

  • The lungs contain millions of alveoli (tiny air sacs).

  • Together, they give a very large surface area for gas exchange.

• Thin walls –

  • The walls of the alveoli and the capillaries are one cell thick, giving a short diffusion distance for gases (oxygen and carbon dioxide).

• Good blood supply –

  • Each alveolus is surrounded by a network of capillaries that constantly bring deoxygenated blood and carry away oxygenated blood, maintaining a steep concentration gradient.

• Moist surface –

  • The inside of the alveoli is kept moist, allowing oxygen to dissolve before diffusing into the blood and carbon dioxide to dissolve before diffusing out.

• Ventilation –

  • Breathing movements (inhalation and exhalation) continuously bring fresh air into the lungs and remove stale air, maintaining a high concentration of oxygen and a low concentration of carbon dioxide in the alveoli.

How the roots are adapted to exchange materials in plants

• Root hair cells –

  • Each root hair is a long, thin extension of an epidermal cell.

  • This gives a large surface area for absorbing water and mineral ions from the soil.

• Thin cell walls –

  • Provide a short diffusion distance, making absorption faster.

• Close contact with soil particles –

  • Allows efficient uptake of water by osmosis and minerals by active transport.

• Many mitochondria in root hair cells –

  • Provide energy for active transport of mineral ions (like nitrates, phosphates, potassium).

How the leaves are adapted to exchange materials in plants

• Large surface area –

  • Increases the amount of light absorbed and allows more gas exchange.

• Thin structure –

  • Short diffusion distance for carbon dioxide to reach the cells.

• Stomata (mainly on lower surface) –

  • Tiny pores that open and close to control gas exchange.

  • Allow carbon dioxide in and oxygen and water vapour out.

• Air spaces in spongy mesophyll –

  • Let gases diffuse quickly between stomata and photosynthesising cells.

• Moist internal surfaces –

  • Enable gases to dissolve and diffuse easily.

• Guard cells –

  • Control the opening and closing of stomata to balance gas exchange with water loss.