Exchange between organisms and their environment (copy)

How do single celled organisms absorb gases such as oxygen?

By diffusion across their body surface.

What have insects evolved to have to aid efficient gas exchange?

• Trachea - network of tubes that split into Tracheoles

• Spiracles

What are the 3 ways gases move in and out the tracheal system?

1. Along a diffusion gradient

2. Mass transport - contraction of muscles squeeze trachea

3. Ends of tracheoles filled with water

What do gases enter and leave the tracheae through?

Spiracles - tiny pores

What features make up the gas exchange system of a fish?

1. Gill arch

2. Gill filaments

3. Gill lamella

4. (Capillaries)

How do blood and water interact in a fishes gas exchange system?

In a countercurrent manner

Why is countercurrent flow beneficial for a fish?

It allows roughly 80% of oxygen in the water to be absorbed whereas parallel flow only allows roughly 50%.

Three ways insects limit water loss.

1. Small surface area to volume ratio

2. Waterproof coverings - rigid outer skeleton covered in cuticle

3. Spiracles

What plants are especially well adapted to limit water loss?

Xerophytes

What are some common ways xerophytes limit water loss?

1. Thick waxy cuticle

2. Rolling up of leaves - traps water vapour so no water potential gradient

3. Hairy leaves - Traps moist air so lowers water potential gradient.

4. Stomata in pits - Trap moist air reducing water potential gradient

5. Reduce S.A to V ratio of leaves - e.g. pine needles

Gross structure of human gas exchange system.

1. Trachea

2. Lungs

• Bronchi

• Bronchioles

• Alveoli

What tissue plays a large role in protecting the respiratory system?

Cartilage - connective tissue found in the ribcage, trachea, and bronchi

How are the lungs adapted for efficient gas exchange?

• Alveoli and capillaries one cell thick - short diffusion pathway

• Many alveoli so large SA

• Lots of blood circulation so maintains conc. gradient

• RBCs are slowed as they pass capillaries

What are the main organs in the digestive system?

1. Salivary glands

2. Oesophagus

3. Stomach

4. Pancreas

5. Ileum

6. Large intestine

7. rectum

What is the role of the stomach?

Produces enzymes, churns food, store and digest food

What is the role of the ileum?

Digestion by enzymes, absorption by epithelial cells

What is the role of the large intestine?

Absorption of water

What is the role of the salivary glands?

Produces saliva that contains salivary amylase.

What is the role of the pancreas?

Secretes pancreatic juice contains pancreatic amylase, lipase, and proteases.

What are the two stages of digestion?

1. Physical breakdown: teeth, stomach→ increase SA

2. Chemical digestion: Enzymes by hydrolysis

What enzymes break down starch?

1. Amylase (to maltose) salivary and pancreatic

2. Maltase (to glucose) membrane-bound disaccharidase

Name 3 membrane-bound disaccharidases.

1. Maltase

2. Sucrase

3. Lactase

Describe the digestion of lipids.

1. Emulsification - Broken down to micelles by bile salts produced in the liver (increases SA)

2. Lipase hydrolyse ester bonds - breaks into monoglycerides and fatty acids

What are the 3 peptidases?

1. Endopeptidases

2. Exopeptidases

3. Dipeptidases

What bonds do endopeptidases hydrolyse?

Bonds between amino acids in central region of chain

What bonds do exopeptidases hydrolyse?

Peptide bonds on the ends of peptidases (remove one amino acid at a time)

What bonds do dipeptidases break?

Peptide bonds between 2 amino acids

What adaptations do the villi possess?

1. Increase SA for diffusion

2. Thin walled

3. Muscle tissue to waft food and maintain concentration gradient with new food

4. Good blood circulation - maintain conc. gradient

5. Microvilli on epithelial cells further increases SA

Describe the process of lipid absorption.

1. Micelles break down on epithelial cell lining

2. Non-polar so easily diffuse through membrane

3. Once in the epithelial cells, monoglycerides and fatty acids transported to endoplasmic reticulum

4. Golgi apparatus aids to associate cholesterol and lipoproteins to form chylomicrons

5. Enter lacteals of lymphatic system then to blood