Biology Paper 2 IGCSE

What does the Xylem carry

Water and mineral ions ( X is close to W)

What does the phloem carry

Sucrose and amino acids (ph sounds like f)

Adaptations of the root hair cells

1. Many mitochondria (for active transport)

2. Long root hair for increased surface area (for osmosis and active transport)

Transpiration definition

Loss of water via evaporation through stomata

6 steps of investigating transpiration

1. Use a potometer

2. Prevent any air bubbles, assemble underwater

3. Leave plant to adjust

4. Measure how far the bubbles move in time

5. Reset bubble position & repeat experiment

6. Alter independent variable

4 components of blood

1. Red blood cells

2. White blood cells

3. Plasma

4. Platelets

Adaptations of red blood cells

1. Biconcave shape for increased surface area

2. No nucleus for more heamoglobin

What substances travel in the plasma

CO2, antibodies, digested nutrients, urea, hormones, mineral ions

Two types of white blood cells

Lymphocytes, Phagocytes

What do Phagocytes do

They engulf pathogens during phagocytosis

What do lymphocytes do

Produce antibodies (Y shaped proteins) which complement antigens on pathogens, and memory cells

What are vaccines and how do they help people

Inject weakened pathogens so that lymphocytes can produce complementary antibodies and memory cells for the specific pathogens

What is blood clotting

Collection of platelets (insoluble mesh) to prevent blood loss and entry of microorganisms

Four heart chambers

1. Left/Right Atrium

2. Left/Right Ventricle

Where do the veins and arteries carry blood

Veins - carry blood to the heart

Arteries - carry blood away from the heart

VEAL

2 features of the heart

1. Left side ventricle wall is thicker to pump blood further

2. Atrium have thinner walls because ventricles are close

3. Septum separates two sides of the heart

Name both arteries on the heart

Pulmonary artery, Aorta

Name both veins on the heart

Plumonary vein, Vena Cava

Effect of exercise on the heart

1. Heart rate increase (more oxygen and glucose needed)

2. Oxygen debt occurs because the heart still needs to pump oxygen to remove lacti

What is CHD and what does it do

Coronary heart disease

Is a block in the coronary artery due to plaque (stopping heart cells from respiring)

What are the causes of CHD

Diet, stress, lack of exercise, smoking, age

Name 3 types of blood vessels

1. Arteries

2. Veins

3. Capillaries

2 adaptations of Arteries

1. Thick muscular, elastic wall

2. Narrow lumen for high blood pressure

2 adaptations of veins

1. Thin muscular wall

2. Wide lumen for less blood resistance

3. Valves to prevent back flow

2 adaptations of Capillaries

1. One cell thick wall for diffusion

2. Very narrow lumen

Excretion products in plants

CO2, Oxygen, Water Vapor

Rate of photosynthesis during the day?

Rate of photosynthesis is greater than the rate of respiration so more O2 released

Excretion definition

Removal of metabolic waste e.g. toxic & excess materials are removed

Excretion products in humans

CO2, Water, Urea, Excess substances (e.g. feaces)

Role of the Kidney

Regulate water content in blood, excrete toxic waste products of metabolism

Osmoregulation definition

Process of maintaining water and salt concentrations across membranes (an example of homeostasis)

What happens if the there is too much water in cells

Cells will swell & cell lysis (burst)

What happens if there is too little water in cells

Dehydrated cells will lead to cell death

Where is water lost in the body

Exhalation, Sweat, Kidney controlling how much is lost

3 structures in the urinary system

1. Kidneys

2. Ureter

3. Bladder

4. Urethra

3 regions of the Kidney

1. Cortex

2. Medulla

3. Renal Pelvis

5 parts of the nephron

1. Bowman’s capsule

2. Proximal convoluted tubule

3. Loop of Henle

4. Distal convoluted tubule

5. Collecting Duct

Where does ultrafiltration happen

Between the Glomerulus and Bowman’s capsule

Where and how does glucose reabsorption happen

In the proximal convoluted tubule through specialized glucose gates (containing may mitochondria) via active transport

Where is water reabsorbed

In the loop of Henle and at the collecting duct, after salt is reabsorbed water will follow due to concentration gradient

Role of ADH

Change in blood levels are detected by osmoreceptors in the hypothalamus which sends signals to the pituitary gland to alter the permeability of the collecting duct

What happens if the water potential of blood is too high

Pituitary gland releases less ADH so the collecting duct is less permeable (less water reabsorbed) dilute urine

What happens if the water potential of blood is too low

More ADH is released so the collecting duct becomes more permeable so more water reabsorbed

3 components of Urine

1. Urea

2. Water

3. Excess Mineral ions

What is a stimulus

A change in the environment that requires a response (e.g.light, temp, sound, touch)