Term 3 Test 1 revision

Question 1

Biosphere

Answer 1

- Consists of the atmosphere, lithosphere, hydrosphere, and biota and interactions between them.
- Interactions within the biosphere include the cylical movement of the essential elements such as carbon, nitrogen, and phosphorus.

Question 2

Atmosphere (Troposphere)

Answer 2

- Layer closest to earth
- Particles of air are packed most closely in this layer and they spread out further away from the surface.
- 6-17 km

Question 3

Atmosphere (Stratosphere)

Answer 3

- Upper atmosphere
- Around 50km thick and contains ozone layer.

Question 4

Hydrosphere

Answer 4

- All of the liquid water on the surface of the earth.
- All water recycled in the water cycle
- Water is an essential part of all living things.

Question 5

Lithosphere / Geosphere

Answer 5

- Land masses on Earth (rocky crust and soil)
- Within this sphere rocks are formed, broken down and changed from one type to another.

Question 6

What is the Carbon Cycle?

Answer 6

- Essential for life on Earth
- Carbon is found in all living things and their dead bodies and waste
- Is the process by which carbon is recycled through the soil, water, living things and atmosphere

Question 7

Carbon Cycle

Answer 7

- The process of photosynthesis in green plants incorporates carbon into living things.
- Respiration releases carbon back into the atmosphere and hydrosphere as carbon dioxide, where it again becomes available for photosynthesis.
- Organisms release carbon into the soil in wastes such as faeces, urine and fallen leaves.
- These wastes are used as food for decomposer organisms.
- As decomposers respire, carbon is released into the atmosphere, water and soil.

Question 8

What is a star?

Answer 8

- The objects that heat and light the planets in a system.
- A star is a ball of plasma held together by its own gravity.
- 3/4 of the material found in a typical star is hydrogen.
- Helium —> Hydrogen

Question 9

Colour and Temperature of a star

Answer 9

- Colour of star indicates temperature.
- Stars are classified by temperature.
- Blue = hot
- Red = cool

Question 10

Distance with stars

Answer 10

- Measured in light-years
- One light-year is the distance that light will travel in one year (approx. 9.5 trillion km)

Question 11

Parallax Effect

Answer 11

- The apparent movement of objects at different distances is due to the actual movement of the observer.
- As the Earth orbits around the sun, the positions of the stars change very slightly relative to each other.
- If all stars were the same distance from Earth, this would not happen.

Question 12

Life cycle of a star

Answer 12

Stellar Nebula —> Average star —> Red giant —> Supernova —> Planetary Nebula —> White dwarf

Stellar Nebula —> Massive star —> Red supergiant —> Neutron star or Black hole

Question 13

Protostar

Answer 13

- First stage in a star’s life
- Formed when gas is pulled together by gravity to form a cloud.
- The protostar continues to condense, it heats up. Eventually, it reaches a critical mass and nuclear fusion begins.
- Begins the main sequence phase of the star (where stars spend most of their lives in this phase).

Question 14

Stars around size of sun

Answer 14

- Main sequence star will expand into what is known as a red giant.
- This phase will last until the star exhausts its remaining fuel.
- At this point, the star will collapse.

Question 15

Star bigger than sun

Answer 15

- Massive stars will become red supergiants
- If the star is massive enough, the collapse will trigger a violent explosion known as a supernova.

Question 16

Causes of variation

Answer 16

- Mutations
- Meiosis
- Gamete combinations
- Gene flow
- Random genetic drift
- Natural selection

Question 17

Species diversity

Answer 17

Number of different species with an ecosystem

Question 18

Genetic diversity

Answer 18

Range of genetic characteristics within a single specie

Question 19

Variation

Answer 19

- Genetic diversity is important because it codes for variations of phenotypes, some of which may better suit the individual organism to a particular environment than others, giving it an increased chance of survival.
- If this individual survives, there is an increased chance of it reproducing to pass the advantageous gene to its offspring, giving them an increased chance of surviving.

Examples of genetic variation include
- Eye colour
- Blood type
- Camouflage in animals

Question 20

Adaptions

Answer 20

- Variations that increase chances of survival may also be thought of as adaptions.
- An adaption may be considered to be a special feature or characteristic that improves and organisms chance of survival in its environment.

Types of adaptions:
- Structural (e.g. fur to keep warm)
- Behavioural (e.g. courtship display to attract a mate)
- Physiological (e.g. ability to produce concentrated urine to conserve water)

Question 21

Step 1: Variation

Answer 21

- Variation of characteristics exists within a population
- Within a single population that is able to interbreed

Question 22

Step 2: Isolation

Answer 22

- Different groups of the population are prevented by some mechanism from interbreeding.
- Isolation prevents gene flow throughout the population, stopping any differences in one population from reaching the other population.

Question 23

Step 3: Selection

Answer 23

- Once isolated by barriers, natural selection affects the genotype and causes changes that prevent the groups from breeding even if they come together again at some time in the future. 
- The isolated populations are now quite different, producing a new species.

Question 24

Divergent Evolution

Answer 24

- Type of evolution in which new species evolve from a shared ancestral species
- Two or more species share a common ancestor
- At some point in history, a barrier has divided the population into two or more populations and also interfered with interbreeding between the populations.