21. Do all parts of Earth receive the same amount of solar
radiation (daylight)?
No. The Earth's axis tilts it at an
angle as it orbits the sun so that the duration of daylight and darkness varies seasonally everywhere except at the equator. This tilt of the Earth's axis affects not only the duration of daylight but also the intensity of the solar
radiation. When the Sun appears directly overhead it's intensity is greatest.
22. What happens to the solar radiation as it passes through Earth's atmosphere?
The atmosphere is made up of gases, particles and clouds. Solar radiation on its way to Earth's surface is affected by these atmospheric components. Some of the radiation (mostly long wavelength) is absorbed by atmospheric gas
molecules. Some of the shorter wavelength radiation is scattered by the molecules, particles and the cloud water droplets. Some of the solar radiation is reflected back into space.
23. Do biological processes rely upon a supply of energy?
Yes. Both plants and animals are absolutely dependent upon energy for growth and movement and for the maintenance of basic function and structure. If energy intake drops below the amount required for maintenance, an organism consumes its own energy stores until those are exhausted and the organism dies.
24. Does all life on Earth depend upon radiant energy from the Sun?
With the exception of certain bacteria and algae which get their energy by the oxidation of inorganic compounds, and the animals that get their energy from these particular bacteria and algae, all life on Earth depends on radiant energy from the Sun.
25. How is solar (radiant) energy made available to living organisms?
Animals cannot use radiant energy but plants can. Chlorophyll molecules in green plants and algae absorb radiant energy (sunlight) and use this energy in the manufacture of glucose (a sugar). The radiant energy is now stored in the glucose molecule as chemical energy and is available to the plant for its growth and to animals when they eat plants.
26. Are plants the only source of energy for animal life?
Yes. Some animals (herbivores or vegetarians) eat plants and derive their energy from the chemical energy stored in the plants' complex carbohydrate molecules. Other animals (predators and scavengers) eat animals, or the remains of animals, who have eaten plants; so, ultimately all animal energy is derived from the radiant energy absorbed by chlorophyll molecules in green plants.
27. Which animals are herbivores and which are predators or scavengers?
Cattle, some insects, and some birds are examples of plant eaters - herbivores or vegetarians. Cats, wolves, spiders, amphibians and reptiles are examples of meat eaters - carnivores or predators. Examples of scavengers - animals that eat the dead remains of other animals - are lobsters and vultures.
28. What is a food chain, and what does a food chain have to do with energy?
A food chain has everything to do with energy. It is a term used by ecologists for the transfer of energy from its usable source in plants (see Day 25) through a sequence of living organisms.
This sequence starts with a plant-eating animal which is the source of food for the animal(s) above it in the food chain.
a) Grasses manufacture complex carbohydrate molecules using solar energy (sunlight);
b) herbivorous animals eat plants in order to obtain that food energy; and
c) carnivorous animals eat herbivores for their food energy.
29. Is photosynthesis the only way that solar energy can be captured in a usable form?
No. Although photosynthesis is so far the only way that solar energy is made available for the maintenance of organic life, scientists have invented solar cells that capture solar energy and transform it to electrical energy. This electrical energy can be used in machines to enable them to do work (cause changge).
30. What is a Btu?
A Btu (British thermal unit) is a universal heat energy unit used to describe the amount of heat necessary to raise the temperature of one pound of water from 60 degrees to 61 degrees Fahrenheit (at sea level).
One Btu is equivalent to 1054.5 joules (see also Number 18).
A joule, named for James Joule, an English physicist (1818-1889), is a another unit of energy equal to a very specific amount of work done when a specific amount of force displaces a specific distance.
31. Do we need to conserve energy?
Yes. Although there is virtually an unlimited amount of solar energy available to Earth, the sources of that energy converted to a usable form are limited. These sources include plant life - humans are gradually covering more and more of the Earth with concrete thus reducing the space for plant life; and oil, coal and gas which exist in specific and limited amounts throughout the world.