Biol4 - Demographic Transition Model and Carbon Cycle

Question 0

During first stage of DT model birth rates are high because? (3)

Answer 0

• lack of contraception
• large families needed to help family provide sufficient food/earn incone
• infant mortality rate, pressure to have many children

Question 1

During first stage of DT model death rate high and fluctuating because? (2)

Answer 1

• limited and unstable food supply

- outbreaks of disease

Question 2

During the second stage of DT model what happens to the death rate and why? (6)

Answer 2

• death rate decreases
• better nutrition with the advent of farming practices, e.g. crop rotation
• food supplies stabalised, therefore reduced deaths due to famine
• better knowledge of spread of disease, e.g. Hand washing in hospitals introduced
• clean water/improved sanitation
• therefore reduction in infectious diseases

Question 3

During the second stage what is the birth rate like and why? (3)

Answer 3

~remains high
~lack of contraception
~large families needed to provide sufficient food/earn income

Question 4

During third stage of DT model what is death rate like? Reasons why? (3)

Answer 4

~Stays low
~vaccination
~improved sanitation as before

Question 5

Third stage of DT model what happens to birth rate and why? (4)

Answer 5

~birth rates fall
~increased availibility of contraception
~requirements of children for labour decreased
~equal job oppurtunities for women, so women have less children

Question 6

What happens to birth and death rates in fourth stage of DMT model? (1)

Answer 6

Birth and death rates stay low and stable

Question 7

How carbon from carbon compounds in dead leaf litter is incoporated into carbon compounds of new leaves (5)

Answer 7

~leaf litter becomes decomposed by saprobiontes through extracellular digestion, saprobionts excrete enzymes (which break down larger organic molecules into smaller soluble ones which saprobiontes can absorb
~saprobiontes use these molecules as substrate for aerobic respiration which releases CO2 into the atmosphere
~CO2 taken up into leaves through stomata
~CO2 used in photosynthesis and the carbon in CO2 is converted to carbon compounds (e.g. Starch)
~some of these carbon compounds are incoporated in new leaves

Question 8

Roles of CO2 and methane (CH4) in enhancing greenhouse effect and bringing about global warming (5)

Answer 8

~CO2 and methane are greenhouse gases
~needed to warm planet up or would be inhabitable
~but in last 200 years amount of CO2 has increased and so have global temperatures
~more greenhouse gases (e.g. CO2) in the atmosphere the more heat is stored in the atmosphere
~so global temperatures rise

Question 9

Give 2 reasons why people in develloped countries have longer life spans than develloping countries (2)

Answer 9

~better healthcare system/vaccinations

~better diet/more food

Question 10

2 reasons why women outlive men (2)

Answer 10

~males involved in war/fighting

~male risk of CVD (cardiovascular disease)

Question 11

Four factors which could lead to a decrease in the death rate in a human population (4)

Answer 11

~improved nutrition
~improved medical care
~less disease
~improved living conditions

Question 12

Proof demographic transition has taken place (2)

Answer 12

~increase in (average) life expectancy

~fewer infants die/lower infant mortality rate