b4 Flashcards
organising animals and plants
Name the four main components of blood.
red blood cells, white blood cells, plasma, platelets
What is the function of platelets?
form blood clots - prevent the loss of blood and stop wounds becoming infected
Why is the human circulatory system a double circulatory system?
blood passes through the heart twice for every circuit
around the body – deoxygenated blood is pumped
from the right side of the heart to the lungs, and the
oxygenated blood that returns is pumped from the left
side of the heart to the body
How does the structure of an artery relate to its function?
carries blood away from the heart under high pressure –
has a small lumen and thick, elasticated walls that can
stretch
How does the structure of a vein relate to its function?
carries blood back to the heart at low pressure –doesn’t
need thick, elasticated walls, but has valves to prevent
blood flowing the wrong way
How does the structure of a capillary relate to its function?
carries blood to cells and tissues – has a one-cell-thick
wall to provide a short diffusion distance
List the structures air passes through when breathing in.
mouth/nose ➞ trachea ➞ bronchi ➞ bronchioles ➞ alveoli
What is the function of the red blood cells?
bind to oxygen and transport it around the body
What is the function of the white blood cells?
defends the body against pathogens
What is the function of the plasma?
transports blood cells and substances around the body
Why is a leaf an organ?
there are many tissues inside the leaf that work together to perform photosynthesis
How is the upper epidermis adapted for its function?
- single layer of transparent cells allow light to pass
through - cells secrete a waxy substance that makes leaves
waterproof
How is the palisade mesophyll adapted for its function?
tightly packed cells with lots of chloroplasts to absorb as
much light as possible for photosynthesis
How is the spongy mesophyll adapted for its function?
air spaces increase the surface area and allow gases to
diffuse quickly
What is the function of the guard cells?
control the opening and closing of the stomata
What is the function of the xylem?
transport water and mineral ions from the roots to the rest of the plant
Give three adaptations of the xylem.
- made of dead cells
- no end wall between cells
- walls strengthened by a chemical called lignin to withstand the pressure of the water
What is the function of the phloem?
transport dissolved sugars from the leaves to the rest of the plant
What is the purpose of translocation?
transport dissolved sugars from the leaves to other parts of the plant for respiration, growth, and storage
Define the term transpiration.
movement of the water from the roots to the leaves through the xylem.
What is the purpose of transpiration?
*provide water to keep cells turgid
*provide water to cells for photosynthesis
*transport mineral ions to leaves
Name four factors that affect the rate of transpiration.
temperature, light intensity, humidity and wind speed
What affect does temperature have on the rate of transpiration?
higher temperatures increase the rate of transpiration
What effect does humidity have on the rate of transpiration?
higher levels of humidity decrease the rate of transpiration
Why does increased light intensity increase the rate of transpiration?
stomata open wider to let more carbon dioxide into the leaf for photosynthesis
What is the function of the stomata?
allow diffusion of gases into and out of the plant
Where are most stomata found?
underside of leaves
What is the advantage to the plant of having a high number of stomata at this location?
reduces the amount of water loss through evaporation
