This is a summary of every learning objective (4.1-4.16) for Topic 4, BNR on the Edexcel Biology A (Salters-Nuffield) specification. I have arranged my notes answering each objective, and have given definitions, core practical information, and equations, based from the textbook.
These notes inc...
BIOLOGY SPECIFICATION NOTES
Edexcel Biology Salters-Nuffield A AS/A-Level
Key:
Definitions are in turquoise
Core practicals are in orange
Equations are in green
Topic 4: Biodiversity and Natural Resources (BNR)
4.1 Know that over time the variety of life has become extensive but is now being threatened
by human activity. p.197
The current extinction rate is higher than any previously recorded geological record. The
primary threat to most species and habitats is human activity. These threats are from:
- Land development (habitat destruction)
- Over-exploitation
- Introduction of alien species
- Pollution
In order to lessen these effects, conservation is needed.
4.2 i) Understand the terms biodiversity and endemism.
Species - a group of organisms with similar morphology, physiology and behaviour. They can
interbreed to produce fertile offspring and are reproductively isolated from other species.
Biodiversity - refers to the diversity within species. It also means the variety of species that
belong to every different group of organism.
Endemism - an organism is endemic if it is only found in one specific defined geographic
location
ii) Know how biodiversity can be measured within a habitat using species richness and within
a species using genetic diversity by calculating the heterozygosity index (H):
The simplest way to measure biodiversity is with species richness. This is simply counting
the number of species present in a given habitat. A very common organism in a habitat is
called the dominant organism.
The heterozygosity index can also be used to measure biodiversity within a species. This is
usually referred to as H, and can be calculated by:
H = number of heterozygotes / number of individuals in a population
, iii) Understand how biodiversity can be compared in different habitats using a formula to
calculate an index of diversity (D): p.173
Biodiversity in different habitats can be compared using a diversity index. This can be
calculated using the formula:
D is the diversity index.
N is the total number of organisms in all species.
N is the total number of organisms in each
species
E means sum of
It measures the number of different species and how evenly individuals are distributed
among those species.
4.3 Understand the concept of niche and be able to discuss examples of adaptation of
organisms to their environment (behavioural, physiological and anatomical). p.154-157
A niche is the way an organism exploits (uses) its environment. Two species living in the
same habitat tend not to be in competition as they occupy different ecological niches. If in
competition, the better adapted organism will out-compete the other.
Organisms adapt in certain ways in order to exploit their own particular niches. These take
the form of behavioural, physiological and anatomical adaptations.
Behavioural
- Actions by organisms that help them survive and reproduce
- Eg. plants turning towards the sun in photosynthesis
- Agoutis burying brazil nuts
Physiological
- Features of the internal workings of an organism that help them survive and
reproduce
- Eg. Danish scurvy grass have adapted a tolerance to high salt concentrations
- Bacteria can survive in high temperature conditions in hot springs
Anatomical
- Structures seen when we observe or dissect an organism
- Eg. Bee has long tongue to suck nectar from flowers
- Pollen basket (hairs) on hind legs
4.4 Understand how natural selection can lead to adaptation and evolution. p.158-160
Natural selection is the survival of organisms that have a characteristic with an advantage
over others, meaning they are the most well adapted to their environment, which causes a
change in species over time. These individuals have a selective advantage. A change in
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