paper 1 Flashcards
Describe how energy for the photosynthesis reaction is gained by plants(2)
absorbs light from sunlight , light is trapped/absorbed by chloroplasts
Explain how the human lungs are adapted for efficient gas exchange by diffusion(6)
Many alveoli provides larger S.A to Volume ratio , Capillaries are thin which provides short diffusion pathway , Breathing in and out to bring fresh o2 and remove co2 , large capillary network to bring in co2 to the lungs and maintain conc gradient
Adaptation of small intestine for both diffusion and active transport(5)
many villi provide large SA , capillaries one cell thick which provides short diffusion pathway , good blood supply to maintain conc gradient , small intestine is long so increased absorption time , cells have mitochondria which provide energy from respirations(ATP) needed for active transport
A woman has children aged 4 , 6 and 9.Why are the children not genetically identical?(2)
Different sperm/egg each time , genes from 2 different parents
A person with AIDS may take longer than a healthy person to recover from salmonella infection. Explain why? (2)
Immune system is weakened , white blood cells cannot kill bacteria
Explain one way in which the root hair cell is adapted to take up water from the soil? (2)
Large surface area , for faster osmosis
Explain why the mean rate of water uptake is higher on a hot day than on a cold day In a plant?(3)
On a hot day more water lost , more transpiration/evaporation , so more water taken up by roots to replace water lost from leaves.
Explain why having one ventricle makes the circulatory system less efficient than having two ventricles?(2)
Oxygenated blood mixes with deoxygenated blood , so less oxygen reaches the body.
A microscope has a ×5 eyepiece lens.
Describe how to use this microscope to observe a prepared slide of root hair cells at a magnification of ×50 ? (6)
place slide on stage
• use lowest power / ×4 objective lens (initially)
• adjust mirror or switch light on so light passes through slide
• move stage as close to lens as possible
• slide must not touch lens
• turn focussing knob so slide moves away from lens
• turn focussing knob until image comes into focus
• use fine focus to get clear image
• change objective lens to ×10
• ×5 eyepiece and ×10 objective lenses (gives total magnification
of ×50)
• refocus slide using focussing knob
Name 2 sites in a plant where you would find meristem tissue?(2)
Tips of roots and tips of shoots.
What is xylem made of? (3)
Xylem is made of dead cells joined together end to end , The walls are strengthened with lignin , the dead cells have no end walls between them so there is a hole down the middle of the tissue.
What is phloem made of ? (2)
Phloem is made of columns of elongated living cells , the cells have small pores in the end walls to allow cell sap to flow through
What is the function of the guard cell?(2)
responsible for opening and closing of stomata , in order to control gas exchange and water loss from a leaf
Name three ways disease can be spread?(3)
Water droplets, by water , by direct contact.
What are the differences between bacteria and viruses?(5)
Virus very small in size, viruses won’t survive outside of host for long, Bacteria larger in size, Bacteria make us feel ill by producing toxins, Bacteria capable of replicating by themselves.
