5.2 Energy transfer and nutrient cycles Flashcards
define producer
photosynthetic organism
define consumer
organisms which obtain energy by feeding on other organisms
define saprobiont
organisms that break down complex materials in dead organisms into simple ones
define trophic level
energy level in a food chain
define food chain
description of feeding relationships
define food web
many interdependent food chains
define biomass
the total mass of living material in a specific area at a given time
how do you measure mass by carbon of an organism?
50% of the dry mass
how do you measure fresh mass of an organism?
weigh the organism
how do you measure dry mass of an organism?
dry out specimen in an oven and weigh at regular intervals, returning it to the oven each time. organism is fully dry when weight remains the same for several intervals. weigh mass of dried organism
how is energy from the sun lost to producers? [4]
- 90% is reflected back
- not all wavelengths can be absorbed
- may not hit chlorophyll
- limiting factor e.g low CO2
define gross primary production
total quantity of energy converted by plants in a given area in a given time
define net primary production
gross primary production - respiratory losses
how is energy lost from the producer to the consumer? [4]
- some parts aren’t eaten
- some parts are indigestible
- excretory materials
- respiration and heat loss
define net production in consumers
consumers get energy from ingesting other organisms
how do you calculate the net production of consumers?
N = I - (F + R)
I = chemical energy in ingested food
F = chemical energy lost in faeces and urine
R = energy lost through respiration
how do you calculate the percentage efficiency of an energy transfer?
percentage efficiency = (energy available after transfer / energy available before transfer) x 100
how does controlling the temperature of animal enclosures reduce energy loss?
energy is not lost through maintaining warmth
how does restricting movement in animal enclosures reduce energy loss?
less energy is lost through respiration
how does feeding animals on controlled diets reduce energy loss?
higher proportion of foo and therefore energy is absorbed by the animals
how does selective breeding of animals reduce energy loss?
genetically selected for high productivity
define pest
an organism that reduces the amount of energy that is available for human consumption
what makes a pesticide effective? [4]
- specific, so only toxic to intended organism
- biodegradable, so breaks down into harmless substances over time whilst still being chemically stable
- cost effective, so can be used liberally
- non accumulative, so doesn’t build up in food chains
define biological control
using a specific predator to reduce numbers of a pest species. aims to reduce levels rather than eradicate the pest entirely. control agent and prey species must exist in balance with one another
