Topic 19

Question 1

overharvesting

Answer 1

When people take so much of an organism that its population is unable to reproduce quickly enough to keep up and the population falls. can lead to extinction

Question 2

energy flow

Answer 2

1. sun source
2. plants use energy from the sun to make glucose during photosynthesis - turn this into biomass (chemical energy store) - transferred to other organisms when they eat
3. biomass and energy is lost in each trophic level
4. some food not eaten - energy taken in/ some parts of food indigestible - removed as waste
5. energy used for staying alive e.g respiration
6. most of the energy transferred as heat to surroundings
7. only 10% of energy in trophic level becomes biomass - 90% is inefficient and lost
8. this is why you never get a food chain with more than 5 trophic levels - so much energy is lost not enough to support more trophic levels. normally you get less organisms in each trophic level.

Question 3

The Carbon cycle

Answer 3

1. plants remove CO2 from the atmosphere during photosynthesis
   - carbon makes glucose = turned to carbs, fats and proteins
   - when these plants respire the carbon is returned to the atmosphere as CO2
2. carbon moves through food chain when animals eat plants
   - when animals respire some carbon is returned to the atmosphere as CO2
3. when plants and animals die they decompose ( decomposers are microorganisms)
   - when they respire they return CO2 to the atmosphere
   - animals produce waste that is broken down by decomposers
4. not all dead organic material decomposes -some is compressed and tuned to fossil fuels
   - combustion of fossil fuels produces CO2
   - carbon constantly cycled

Question 4

Nitrogen cycle

Answer 4

1. 78% of the atmosphere contains Nitrogen gas - needed for making proteins for growth
2. Nitrogen in air has to be turned into an ion to be used through a process called NITRGOEN FIXATION:
   - Lightning: enough energy to make Nitrogen react with oxygen to give nitrates
   - Nitrogen Fixing Bacteria: in soil and roots of some plants
3. plants absorb the ions from the soil and nitrogen in them to produce amino acids that make proteins
4. Nitrogen passed along food chains as proteins, animals eat these. when they are digested they convert back to amino acids
5. in animals excess amino acids are broken down in the liver through deamination and this gets excreted through urea. urea decomposes and nitrogen returned to soil.
   - DECOMPOSERS: break down proteins and urea and tun them to ammonium
   - NITRYFYING BACTERIA: turn ammonium ions into decaying matter into nitrate ions and nitrates. (nitrification)
   - NITROGEN FIXING BACTERIA: turn atmospheric nitrogen into nitrogen compounds that plants can use
   - DENITRYFING BACTERIA: turn nitrates back to nitrogen gas. no benefit to living organisms.