Summary Environmental Studies Grade 12 Life Science (Biology)
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Module
Life Sciences
Institution
12th Grade
These notes are provide detailed information on the environmental studies chapter in the Mind Action Series Life Science Grade 12 textbook. These notes are colourful, have diagrams for further explanation and are very easily understood.
Module 1
Population Ecology Population growth regulation
Unoccupied area w/ x food / resource
Definition: shortage & x predators – will reprod &
o concerned w/ fluctuations in individual numbers incr exponentially
size of population & factors, ➢ # incr ∴ more demands = made ∴ builds up
both physical & social that environmental resistance
regulates these fluctuations environmental resistance = total # of
factors that stop pop from reproducing @
Ecology = study of interactions of max rate
organisms w/ physical & biological ➢ Balance = reached ∴ pop stabilizes @
environments certain size/#
➢ individuals → populations → ➢ # = carrying capacity of ecosystem
communities → communities w/ non-
living environ = ecosystem → biosphere carrying capacity = population density
that environment can support
Biosphere = part of earth where living
organisms are found Pop fluctuates around carrying capacity
until environ changes
Ecosystem = made up of groups of diff
species of organisms w/ their environment o Pop size fluctuates seasonally & annually
depending on resources available
Community = a group of diff species that
inhibit & interact in a particular area o Pop size of ecosystem = self regulating
o = negative feedback system
Population = a group of organisms of the
same species that occupy the same area &
can be breed freely w/ e/o Limiting Factors
Individual = a single organism capable of
independent existence Definition:
o Factors that help regulate the
Species = a group of closely related
organisms that = very similar to e/o & = growth of a population
capable of interbreeding & producing fertile
offspring TYPE OF FACTORS
WHAT AFFECTS POPULATION SIZE 1. Density independent factors
o Limit pop growth bcz result of
natural factors
Definition: ➢ Physical factors = rainfall,
o total number of individuals in a temperature, humidity, acidity, salinity
population ➢ Catastrophic factors = floods, fire,
drought, volcanic eruptions, tsunami,
➢ Can incr / decr over time w/ earthquakes
change in natality, mortality,
immigration & emigration 2. Density dependent factors
o Have greater effect when pop
natality = birth rate in animals / density = high
production of seeds in plants o Organisms = crowded ∴
➢ Compete for resources (food, light,
mortality = death rate O2, H2O, space & shelter)
➢ More easily found by predators
immigration = individuals move into a
➢ Spread disease & parasites more
population & stay readily
emigration = individuals leave a factors build up environmental resistance
population & x return
➢ Natality & immigration > mortality { stable + unstable populations }
& emigration ∴ pop grow Stable = # decr when size exceeds carrying
, Module 1
Population Size Estimation Predator-Prey Relationships
measure size of pop to see if living orgs in ecosystem =
changing over time interdependent
{ direct methods } predation = biological interaction
where 1 species, predator, kills & eats
Census = counting every single another species, prey
individual in population o evolve together & = part of same
used for individuals that = environment
1. slow moving Predators create & maintain
2. stationery
greater diversity w/in ecosystem
1. Regulate abundance & distribution of
3. stay in fixed position prey species
Area = too large therefore use: 2. Incr biodiversity of communities by
preventing single species from becoming
1. Aerial photographs = taken to dominant
show whole area
3. Keeping prey population fit by removing
2. Helicopters = used to count larger sick, injured & weak individuals
animals 4. Providing vital food sources for
scavengers
{ indirect methods }
counting a sample number of population
then using calculation to estimate total
size of population
Quadrat method
summary:
# 𝐢𝐧 𝐬𝐚𝐦𝐩𝐥𝐞 𝐱 𝐬𝐢𝐳𝐞 𝐨𝐟 𝐡𝐚𝐛𝐢𝐭𝐚𝐭 o prey ↑, pred ↑
𝐍= o pred ↑, prey ↓
𝐬𝐢𝐳𝐞 𝐨𝐟 𝐪𝐮𝐚𝐝𝐫𝐚𝐭 o prey ↓, pred ↓
Used to enable comparable samples to be o pred ↓, prey ↑
obtained from areas of consistent size & shape
o Random sampling = NB bcz distribution of
individuals may x be uniform Food Webs
Mark-recapture method Definition:
𝑴𝒙𝑪 o interconnected set of all the
𝐏= food chains in an ecosystem
𝑹
P = estimated population ➢ made up of carnivores, herbivores,
M = total # of marked animals omnivores, producers, scavengers &
decomposers
C = total # caught in 2nd sample
- keep ecosystem healthy & balanced
R = total number of marks in 2nd sample
FOOD WEB EXAMPLE
Used for animals that are:
1. Mobile
2. Not easily visible
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