The heart is a muscular organ of the size of a fist, located behind the breastbone and just a little to the left. The cardiovascular system is known as the heart pumps blood through the network of arteries and veins.
⦁ To allow blood to circulate only one way.
⦁ To stop blood backflow.
⦁ Oxygenated blood (from lungs to body) is known as the blood supplying oxygen.
⦁ Deoxygenized blood (from the liver to the lungs) is the blood that does not contain oxygen.
⦁ The left side of the heart is larger and muscular, as the blood is pumped into all parts of the body.
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The Blood Vessels
Three kinds of blood are available:
⦁ Capillary. (Small)
Differences Between Arteries and Veins.
⦁ The central cavity is narrower than the nerves.
⦁ The elastic and muscular wall of the arteries is larger than the veins.
⦁ Although the arteries have no valves, the veins have valves.
⦁ The blood flows slowly and deeper than the lungs under low pressure.
⦁ Oxygenated blood is found in all arteries except the PU, while deoxygenated blood is borne in every vein except the pulmonary veins.
⦁ Blood from the heart is carried by the arteries to the corpse while blood from the veins is translated to the heart.
⦁ The blood in the lungs is light red while the blood in the bones is deep purple.
⦁ Blood pools through the lungs due to the heart’s pumping action as the muscles flow because of the cardiac contraction.
⦁ Blood Components:
⦁ Blood cells. Cells contain blood.
⦁ Plasma is a flowing blood component containing:
⦁ Blood cells. Cells contain blood.
⦁ Water. Water.
⦁ Proteins in the body.
⦁ Products of waste.
⦁ Glucose, sugars, vitamins, and so forth, diets.
⦁ There are two categories of blood cells:
⦁ Red blood cells.
⦁ White blood cells.
⦁ Red blood cells are also called erythrocytes that carry oxygen. White blood cells are also used to transport oxygen.
⦁ White blood cells have the role of a defensive system as leukocytes.
⦁ The role of blood clots is platelets known as thrombocytes. (including fibrinogen utilization)
⦁ Eight. Fibrinogen is used to form fibrin in conjunction with platelets.
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Transpiration is the mechanism by which the plant leaves wastewater. This is a process by which plants lose water in the form of water vapor mainly through leaves to the atmosphere. Transpiration can also occur from flowers.
Types of transpiration
1. Stomatal transpiration: This is the transpiration through the stomatal opening. This contributes up to 80-90% of water lost.
2. Cuticular transpiration: This occurs through the leaf cuticle which amounts to about 20% of the water lost.
3. Lenticular transpiration: This occurs through the stem pores called lenticels and accounts for about 0.1% of the water lost.
Water can also be lost from the plants as water droplets in a process called guttation through special structures called hydrates found on leaf types or margins.
Factors that affect the rate of transpiration
Temperature: Temperature increase increases the sweating rate.
This is due to the latent heat in high temperatures which increases the water evaporation leading to more water being lost.
The kinetic energy of the air molecules around the blade is further increased by temperatures which allow them to move farther apart and hence increases the diffusion rate from the blue.
2) Relative humidity: The sum of oxygen in the atmosphere is water vapor. The rate of transpiration decreases with increased humidity. That is how water vapor saturates the atmosphere. The water will then be drained by the decrease of plants, raising the transpiration rate.
3) Wind: The rate of transpiration is higher in windy air than in still air. This is because wind helps / assists to remove water vapor in the air around the leaf and creates more spaces that can take up more water vapor.
4) Light intensity: The rate of transpiration is high in the presence of light and glow in the dark. This is because high light intensity results in a high rate of photosynthesis which increases the sugar concentration in the guard cells which leads to the wide opening of the stomata leading to more evaporation from the plant (also light provide heat which increases evaporation from the leaf stomata.
5) Atmospheric pressure: Humidity decreases with a decrease in atmospheric pressure. Hence decrease in atmospheric pressure greatly increases the rate of transpiration due to decreased humidity.
6) Distribution of stomata: The rate of transpiration is low when more stomata are on the lower side and is higher when more stomata are on the upper side of the leaf.
7) Number of stomata: The greater the number of stomata, the higher the rate of transpiration because more water vapor is lost through the stomata.
8) Surface area for transpiration: Plants with wide/broad leaves have a larger surface for transpiration thus they experience a higher rate of transpiration.
9) The thickness of the plant cuticle: The rate of transpiration decreases with an increase in the thickness of the cuticle. For that reason, plants found in deserts have an extremely thick cuticle than those in tropical regions.
Experiments to measure the rate of transpiration
1. The weighing method:
2. Photometer method:
This is done using an instrument called a photometer. The photometer works on the assumption that water lost from the leaves during transpiration equals water absorbed by the plant.
Therefore, the photometer:
⦁ Directly measures the rate of water uptake/ absorption of the shoot and
⦁ Indirectly measures the rate of water loss/evaporation of water/ transpiration from the leaves.
⦁ A leafy shoot of a plant is cut underwater to prevent air bubbles from entering as these would block the xylem vessels.
⦁ The photometer is filled with water.
⦁ The leafy shoot is fixed into the cork and then fitted into the mouth of the photometer vessel.
⦁ Vaseline is smeared at the interface of the shoot and the cock to prevent the entry of air into the apparatus.
⦁ A single air bubble is introduced at the open end of the capillary tube by touching the open end briefly underwater and then release.
⦁ At a given mark P, reached by the air bubble, a clock is started and after a given time t, the new position of the air bubble Q is noted and recorded.
⦁ In any given set of environmental conditions, about 3 experiments can be performed, resetting the air bubble after each experiment by opening the tap and then close.
⦁ The average rate is then calculated and taken as the rate of transpiration in that environment.
⦁ The set up can be moved to different environmental conditions and the rate of transpiration determined in the same way.
Precautions are taken when using a photometer to ensure accurate results
A leafy shoot should be used to ensure significant water loss.
The shoot must be cut underwater to prevent air from entering and blocking the xylem vessels.
The whole apparatus must be full of water.
A single air bubble must be present in the capillary tube for each experiment.
Air bubble must be reset to zero marks before each experiment
A graduated capillary tube must be used to read the results.
Air bubble should not cross the T- function at the reservoir
Adaptations of plants to reduce transpiration rate
⦁ Dispersion of leaves of deciduous trees, since most of them arise from the leaf. Structural changes in the stomachs, i.e. some trees are stomached and others have hairy stomachs that limit their evaporation.
⦁ Reduction in the structure of the leave i.e. certain plant leaves is reduced into thin or narrow structures of the spines, reducing the surface area of transpiration.
⦁ Rolling of leaves around your stomach to create a moist atmosphere, reducing the loss of water.
⦁ Changes in the stomach opening rate i.e. close during daytime and open in the night at very low temperatures.
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Importance of transpiration
Results in the absorption of water and its movement up the plant to aid processes like photosynthesis.
Contribution to maintenance of continuous stream of water throughout the plant.
Transported water keeps the plant cells turgid and cools the plant.
Results in the movement of mineral salts up the plants to where they are needed.
Excessive water loss from the plant may lead to wilting, drying, and even death of the plant.
Water may lead to overcooling which affects metabolic activities.
Over absorption of mineral salts with water lead to soil exhaustion.