Saturday, July 14, 2012

NOVEMBER O LEVEL TIMETABLE 2012

9-Oct IRK 1 2047/1 AM
25-Oct Bio 3 5090/32 PM
English 1 1120/12 PM

29-Oct Bio 2 5090/22 PM
11-Oct Phy 2 5054/22 PM
Com Sc 2 5129/22 PM

15-Oct IRK 2 2047/2 AM
30-Oct Geo 2 2230/2 AM
Chem 2 5070/22 PM
POA 1 7110/12 PM

16-Oct English 2 1120/22 PM
5-Nov Geo 1 2230/1 AM

DMaths2 4024/22 PM
17-Oct BM 2 1201/2 PM

8-Nov Amaths 1 4037/13 AM
18-Oct BM 1 1201/1 AM
Phy 3 5054/32 PM
14-Nov Amaths 2 4037/23 AM

Chem 1 5070/1 PM
22-Oct POA 2 7110/22 PM

15-Nov Com Sc 1 5129/1 PM
23-Oct Chem 3 5070/32 PM
Phy 1 5054/1 PM

24-Oct DMaths1 4024/12 PM
16-Nov Bio 1 5090/12 PM

Friday, July 6, 2012

CONTINUATION- MAY/JUNE 2012 PAPER 2 ANALYSIS

SECTION B

QUESTION 6

a) Describe the structure of a seed, stating the functions of the features you mention.
ANSWER:
seed coat/testa- protect the seed
micropyle- small opening that allows water to enter the seed
cotyledon- seed can have one or two cotyledons, which is the source of food when the seed is germinating

b) Describe and explain the processes that occur when a seed germinates

ANSWER:
1) water enters the seed through the micropyle
2) water activates enzymes, causing conversion of insoluble food molecules (starch, protein, fats) to soluble food molecules (glucose, a. acids, f.acids and glycerol)
3) Glucose used for respiration, a.acids use for growth of protoplasm, f.acids and glycerol for energy and making of cells

QUESTION 7

a) Explain what is meant by the term pyramid of numbers

ANSWER:
A diagram showing the numbers of organisms at each trophic level in a food chain. The bottom level is the producer, followed by the primary consumer, secondary consumer and tertiary consumer. The pyramid can be broad based and narrow towards the top, narrow based at the bottom if there is only one producer (a tree) and then becoming narrow at the top, or having the top level broader than the level just below it, showing that the top level are parasites.

b) Explain the fact that energy flow is non-cyclical.

ANSWER:
In any ecosystem, the ultimate source of energy is the sun. The energy is passed from producers to consumers, and is used for growth and other metabolic activities of the organisms. Energy is also lost as heat energy but this heat energy cannot return to to the same system or the organisms that produced it.
Dead organisms and egested and excreted materials are broken down by decomposers, releasing chemical energy which is used by the decomposers or enter the soil. The rest of the energy is lost as heat.
Eventually, all energy that enters the biotic part of the ecosystem is lost as heat energy, which cannot be used by organisms.


QUESTION 8

ai) Explain the term osmosis

ANSWER:
The movement of water molecules from a solution of higher water potential to a solution of lower water potential, down a concentration gradient, across a selectively/partially/semi permeable membrane

ii) Explain the ways in which active transport is different from osmosis

ANSWER:
Active transport involves movement of molecules/ions
UP a concentration gradient
with the use of energy (in the form of ATP)
can only occur in living organisms (only living things can respire to liberate energy)

b) Explain how it is possible for oxygen in the lungs to diffuse rapidly into the blood.

ANSWER
-capillary walls and alveolar walls are thin, reducing diffusion distance
-blood flow in capillaries is in one direction, always maintaining a low concentration of oxygen around the alveoli, while directing oxygenated blood away from the alveoli


QUESTION 9

a) Describe the removal of excretory products from the human body

ANSWER

Excretory products: waste from metabolic activities

Carbon dioxide: produced from respiration; removed by the lungs; blood carrying high concentration of carbon dioxide is sent to the lungs, CO2 will diffuse into the alveoli (which has a lower conc. of CO2) , and is exhaled out of the lungs

Urea: produced in the liver by deamination of excess amino acids; sent to the kidneys via the blood; blood undergoes ultrafiltration- removes urea from the blood; useful products get selectively reabsorbed back into the blood, but not urea... mixes with excess water and salts to form urine which is expelled through the urethra; small amounts of urea can also be excreted through sweat

Water: produced from respiration; removed with the urine, removed through sweating via the skin, or through air exhaled by the lungs.

b) Explain why the removal of faeces is not regarded as excretion (this question has come out so many times!!!!!)

ANSWER

Excretion is the removal of metabolic waste products from the body. Faeces are not metabolic waste, instead they are undigested food that have never been metabolised by the body, so they are not excreted from the body, but egested (process is called egestion)