WhatsApp MR Beacon Chapterz 0546215469

*_SECTION A_*

*1. (a)* Explain *briefly* how soil water gets to the leaves of a plant.

*(b)* State *five* reasons for classifying organisms.

*(c)* Explain *briefly* how the following structures of mammals are adapted to their functions:

*(i)* veins;

*(ii)* arteries.

*2. (a) (i)* Define enzymes.

*(ii)* State *five* characteristics of enzymes.

*(b)* Describe *briefly* the role of the pancreatic juice in the digestion of carbohydrates and proteins in mammals.

*(c)* A student fractured a leg, the leg was put in a cast and the student was advised to drink plenty of milk and spend some time under the sun.

Explain *briefly* the reason for the instructions.

*(d)* State *five* ways in which photosynthesis is of importance to humans.

*3. (a) (i)* Name *three groups* of microorganisms.

*(ii)* Give *one* example of each group.

*(iii)* State *four* ways by which microorganisms can be controlled.

*(b)* List *four* abiotic factors that affect an animal living at the bottom of the sea.

*(c) (i)* List *three* human activities that may lead to extinction of species in an area.

*(ii)* State *three* adverse of the extinction of a plant species on humans.

*4.* In maize species, starchy grain *(GG)* is dominant to sugary grain *(gg)*. *Two* pure maize varieties were crossed, one grown from a starchy grain and the other grown from a sugary grain.

*(a) (i)* With the aid of genetic diagram, determine the phenotype of *F1* grains.

*(ii)* The *F1* grains grew into mature plants and were allowed to self pollinate.

What is the expected ratio of starchy to sugary grains on the cobs borne on the *F2* plants?

*(b)* If the total of *F2* grains collected is *580*, how many of these would be expected to be:

*(i)* starchy;

*(ii)* sugary.

*_SECTION B_*

*5. (a)* Describe the _Watson and Crick model of DNA_ structure.

*(b)* Describe briefly the method of feeding in _Rhizopus._

*(c)* In a tabular form, outline *three* difference between *two* named classes of _Bryophyta._

*(d)* Name *three* sources of:

*(i)* energy which do *not* depend on fossil fuel;

*(ii)* biological fuel.

*(e)* Describe the structure of the cartilage found in mammals.

*(f)* In a tabular form, state *four* difference between a dicotyledonous stem and a monocotyledonous root.

*_SECTION C_*

*6. (a)* Explain *briefly* the following adaptive behaviours giving one example in each case:

*(i)* mimicry;

*(ii)* camouflage.

*(b)* State three structural features that adapt cockroach to its habitat.

*(c)* State *two* effects of pests on plants.

*(d)* List *four* methods of preserving food.

*(e)* List *two* applications of variation in a human society.

*(f)* State *four* factors that could lead to competition in a plant population.

*(g)* Explain the term _succession._

*(h)* State three disadvantages of burning vegetation before cropping