SCIE 3001
Question 01 - Living Things
Question 02 - Living Things
Question 01 - Ecosystems
Question 02 - Ecosystems
Question 01 - Earth Sciences

Question 1 - Earth Sciences

1. (a) Your students would like to know why we have day and night. Explain this phenomenon and the hands-on activity to illustrate it.
6 marks
(b) Describe fully the formation of soils.
6 marks
(c) How will you distinguish between sandy soil, clay soil and silty soil on the basis of their particles?
6 marks
(d) What do you understand by the Heliocentric and Geocentric Model of the Solar system?
3 marks
(e) With the aid of a diagram, explain the terms vent, crater and magma.
4 marks

day and night

Fig 1.

(a) We have day and night because the Earth:
1. Spins on its axis, which is an imaginary line passing through the North and South Poles.
2. The side of the Earth facing the Sun is bright and called day.
3. The side of the Earth away from the Sun is dark and called night.
4. The Earth completes a rotation every 24 hours so day and night should be 12 hours each.
5. Extension - Day and night may be longer or shorter because the Earth’s axis is tilted and in summer days are longer and nights are shorter. The opposite happens in winter.

Hands-on Activity.
Resources – Globe and torchlight.
Make the classroom dark enough so that the area over which the torch shines is lit up and the opposite side of the globe is dark. Shine the torch on the globe and let children observe that one side is bright and the opposite side is dark. Slowly spin the globe and children observe how the bright area moves. Explain that the torch represents the Sun and the globe the Earth so that as the Earth rotates on its axis one side is bright (day) and the opposite side is dark (night).


(b) Five factors determine the type of soil formed.  The soil is always the same wherever these five factors are the same, however, a different soil will be formed if one or more of the factors change. The factors are:
1.  Parent material or Bedrock
2.  Climate
3.  Biological factors
4.  Topography
5.  Time
Parent material is made of rock and minerals. The other four soil-forming factors act on parent material to weather it into smaller particles. The physical weathering processes that break up parent material into smaller particles to form soil include:

  1. Temperature changes — freezing and thawing.
  2. Erosion by water, wind, ice and gravity.
  3. Roots of plants, burrowing animals, insects and microorganisms.
  4. Water relations — wetting and drying.

The chemical weathering processes involves changes in chemical composition by reaction between minerals and also air and water.
Climate - The amount of water entering a soil influences the movement chemical compounds in the soil and thus determines the depth and nature of the soil. Precipitation influences vegetation and thus defines the organic matter content of soils. Higher temperatures can speed the rate of organic matter decomposition.
Biological factors – Plant’s root systems, size, above ground vegetative volume, nutrient content and life cycle determines the kind of soil developed. Detritivores also determine soil minerals.
Topography - Variations in topography affect moisture and temperature relations.
Time - Soils are young, mature, and old, depending on the degree of weathering so soils evolve to a mature state when it is is in equilibrium with its environment.

(c) Sand, silt and clay are the three basic types of soil. Since most soils are composed of a combination of these different types the mix will govern the texture of the soil.
Sand is fairly coarse with the largest particles and loose so water is able to drain through it easily. This allows good drainage, but poor water or nutrients for growing plants. It is dry and gritty to the touch.
Silty soil has smaller particles than sandy soil and is smooth to the touch. When moistened, it feels soapy slick. Dry silt feels almost like flour. When rolled between the fingers, a layer adheres to the skin. Silty soil retains water longer than sand, and is fairly fertile.  
Clay has the smallest particles among the three. It’s sticky to the touch when wet, but smooth when dry. There is very little space between the fine grains for air or water to circulate. Consequently, clay does not drain well or provide space for plant roots to flourish.
Extension - Loam it is really a combination of sand, silt and clay. It can be moulded it into a ball, but easily crumble when disturbed.

d) The heliocentric model places the Sun as the centre of the universe with the planets orbiting around it. This model replaced the belief that the Earth is the centre of the universe which is the geocentric theory. Heliocentrism gained popularity in the 1500’s because it better explained the evidence emerging from developing technology and detailed celestial observations by astronomers like Nicolaus Copernicus. Though opposing ideas existed, the geocentric model was developed in Ancient Greece spreading throughout Europe, and other parts of the world for centuries with the dogma of the Catholic Church. The Roman Catholic Church, at that time considered to be source of what was true and false labelled the heliocentric model as heretical. Galileo was kept him under house arrest for the last eight years of his life when the Church arrested him for promoting the heretical heliocentric model. Galileo invented the telescope and astronomer Johannes Kepler refined the heliocentric model with mathematical calculations. A new way of thinking was emerging called the Scientific Revolution which viewed the natural world through the lens of observation and experimentation of reliable and repeatable phenomenon rather the authority of philosophers. As new evidence appeared the Sun is not actually the centre of the universe. Neither is the Sun is at the geometric centre of the planets’ orbits.


Fig. 2.

(e) Vent – A volcano’s main vent is the point on the Earth’s crust where hot magma has reached the  surface. Volcanoes build up as ash, rock and lava ejected during eruptions fall back to Earth around the vent. On large volcanoes, magma will reach the surface through several different vents forming secondary cones.
Crater – Located at the bottom of the crater a volcanic crater is a circular depression in the ground.
Magma – Magma is a large underground pool of molten rock sitting underneath the Earth’s crust. Less dense than the surrounding mantle it oozes up to the surface through fissures and faults in the crust. When magma emerges from the vent it is called lava.
Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.