B04a) ORGANISING ANIMALS
The heart pumps low oxygen/high carbon dioxide blood to the lungs
Lungs and gas exchange
Trachea | Carries air to/from the lungs | Rings of cartilage protect the airway. |
Bronchioles | Carries air to/from the air sacs (alveoli) | Splits into multiple pathways to reach all the air sacs. |
Alveoli | Site of gas exchange in the lungs | Maximises surface area for efficient gas exchange. |
Capillaries | Allows gas exchange between into/out of blood | Oxygen diffuses into the blood and carbon dioxide diffuses out. |
Heart
Different structure in the heart have different functions | Right ventricle | Pumps blood to the lungs where gas exchange takes place. |
Left ventricle | Pumps blood around the rest of the body. | |
Pacemaker (in the right atrium) | Controls the natural resting heart rate. Artificial electrical pacemakers can be fitted to correct irregularities. | |
Coronary arteries | Carry oxygenated blood to the cardiac muscle. | |
Heart valves | Prevent blood in the heart from flowing in the wrong direction. |
The heart is an organ that pumps blood around the body in a double circulatory system
Artery | Vein | Capillary |
Carry blood away from the heart | Carry blood to the heart | Connects arteries and veins |
Thick muscular walls, small lumen, carry blood under high pressure, carry oxygenated blood (except for the pulmonary artery). | Thin walls, large lumen, carry blood under low pressure, have valves to stop flow in the wrong direction, carry deoxygenated blood (except for the pulmonary vein). | One cell thick to allow diffusion, Carry blood under very low pressure. |
Blood vessels
Blood
Plasma (55%) | Pale yellow fluid | Transports CO2, hormones and waste. |
Red blood cells (45%) | Carries oxygen | Large surface area, no nucleus, full of haemoglobin. |
White blood cells (<1%) | Part of the immune system | Some produce antibodies, others surround and engulf pathogens. |
Platelets (<1%) | Fragments of cells | Clump together to form blood clots. |
Blood is a tissue consisting of plasma, in which blood cells, white blood cells and platelets are suspended
B04b) ORGANISING PLANTS
The roots, stem and leaves form a plant organ system for transport of substances around the plant
Plant organ systems
Epidermal tissues | Waxy cuticle (top layer of the leaf) | Reduces water loss from the leaf |
Guard cells and stomata | Guard cells open and close the stomata to control water loss and allow for gas exchange (oxygen and carbon dioxide). | |
Palisade mesophyll | Palisade cells | Cells near the top surface of the leaf that are packed with chloroplasts that contain chlorophyll. Both adaptations maximize photosynthesis. |
Spongy mesophyll | Air spaces in the leaf between cells | Increased surface area for gas exchange so that carbon dioxide can diffuse into photosynthesising cells. |
xylem | Hollow tubes strengthened by lignin adapted for the transportation of water in the transpiration stream | Allows transport of water and mineral ions from the roots to the stem and the leaves. |
phloem | Cell sap moves from one phloem cell to the next through pores in the end walls | Transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage (translocation). |
Meristem tissue | New cells (roots and shoot tips) are made here including root hair cells | Root hair cells have an increased surface area for the uptake of water by osmosis, and mineral ions by active transport. |
Plant tissues
xylem
nucleus
cytoplasm
cell membrane
cell wall
permanent vacuole
phloem
Transpiration | The rate at which water is lost from the leaves of a plant. The transpiration stream is the column of water moving through the roots, stem and leaves | Temperature, humidity, air movement and light intensity affect the rate of transpiration. |
Transpiration
The shape of the graph for light intensity is the same for temperature (energy)
A potometer is used to measure the amount of water lost over time (rate of transpiration)