BIOLOGY OBJECTIVES
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GCE EXPO

THEORY BIOLOGY

2ai)An Enzyme is an organic catalyst, usually proteinous in nature, which promotes or speeds up chemical changes in living cells but are not themselves used in the process



2aii)-All Enzymes are proteins in Nature
-Enzymes are usually involved in reversible reactions
-Enzymes are affected by the pH (acidity or alkalinity) of their surrounding. They are destroyed by strong acids or alkali
-Enzymes accelerate the rate of chemical reaction
-Each Enzyme is specific in action I.e. An Enzyme or a group of enzymes deals with only one process


6a)
i)mimicry is a similarity of one species to another that protects one or both.
An example of this is the cuckoo bee.
ii)Camouflage is the structural adaption that enables specie s to blend with their
surroundings; allows a species to avoid
detection by predators.
6b)
i)Their legs are adapted for running
ii)They adapts the leathery forewings as
temina to provide a protective cover for the second set of wings.
iii)they evolved mandibles to bite and chew solid food.
6c)
i)It reduces the quality and quantity of the crops
ii)it reduces their productivity
6d)
i)by refrigerating
ii)by salting
iii)by drying
iv)by the use of silos
6e)
i)in medicine
ii)in crime detection


6f)
i)Inadequate resources
ii)Small planting space
iii)
6g)
Succession is the change in either species
composition, structure, or architecture of
vegetation through time.
6h)
i)it kills microorganisms
ii)It leads to soil erosion
iii)It lost of soil nutrients


1a) A plant has roots which extend into the soil. Attached to these roots are small hairs, called root hairs which increase the surface area of the root and allow the root to take up water more easily. Water moves into the roots by osmosis which requires no energy since the water concentration is greater outside the plant then inside the plant's roots."Once inside the root hair, the water needs to be transferred to the xylem, the vascular tissue involved in water transport through the plant. In roots, the vascular tissue is found in a central column, separated from the cortex parenchyma cells by a single layer of cells called the endodermis

There is a water concentration gradient across the root which means that water which has entered the root hair cell continues to move across the cortex to the endoderm
is by osmosis. The route taken by much of the water is through the cellulose cell walls, the rest of the water either passes through the cytoplasm of the cells or via the cell vacuoled once it reaches the endoderm cells, the water is forced to move through the cytoplasm.

This is because the radial and transverse cell walls of the young endoderm is are impregnated with an impervious material. This is known as the Casperian strip, its presence means the route throughthe cell walls is blocked.

The gradient of water concentration that exists across the cortex creates a pushing force called "root pressure", i.e. a pressure that "pushes" the water across. Root pressure can be demonstrated by cutting a stem atsoil level, after a time, droplets of water can be seen exuding from the cut surface. In some plants the process occurs naturally as"gustation", when droplets of water are forced through special pores (hydathodes) on the leaf edges.

It is likely that the process of root pressure requires energy, as metabolic poisons halt the process."