Biology : Term 2 Grade 11
The Scientific method
HYPOTHESIS TESTING
● WHAT IS A HYPOTHESIS?
- An attempt to explain some event or observation using whatever information
is currently available.
- It is a testable statement that may be supported OR not supported.
- Must: Have two variables (dependent and independent variables);
- State the relationship between the two variables;
- State the independent variable first (cause) and then the dependent variable
(effect).
- A hypothesis DOES NOT have to be a correct explanation of the
event/observation.
● Your DEPENDENT and INDEPENDENT variables should be IDENTIFIED
from the AIM OF THE INVESTIGATION AND...... your CONCLUSION
should ALSO be identified from the AIM of the identification.........
● INDEPENDENT VARIABLE
- Refers to the factor that is being investigated.
- This factor is usually manipulated / changed by the investigator either at the
start of or during the course of the investigation.
- The investigator decides what to test.
- The independent variable appears on the X-axis of a graph.
- Which factor did we CHANGE?
● DEPENDENT VARIABLE?
- Refers to the effect of the independent variable.
- This effect is usually measured or observed in some way and appears on the
Y-axis of a graph
- The results investigator is waiting for.
- Which factors did we MEASURE?
● CONSTANT/FIXED variables
- Which factors did we keep THE SAME?
● VALIDITY
- Validity questions show how the experiment/investigation was carried out.
, - It is important to be sure that all the factors/variables have been
controlled/fixed EXCEPT THE VARIABLE/FACTOR BEING TESTED.
- In questions which require learners to suggest some factors that might have
decreased the validity of an investigation, the answers should centre on the
criticism of the scientific process; for example, some factors/variables that
were not fixed/controlled when carrying out the investigation.
- FIXED VARIABLES LEAD TO VALIDITY
● RELIABILITY
- Repeat the investigation,
- Increase the sample size,
- Take many readings and use average, Select a random sample,increase the
period of the investigation.
● GRAPHS
- Heading
- y-axis = dependent variable
- x-axis = independent variable
- scale
- type of graph = line, bar, histogram, circle
- plot of data
● TABLES
- Heading
- Left column = independent variable
- Right column = dependent variable must have lines corresponding data must
be in line measuring units !!!
BIODIVERSITY IN ANIMALS:
THE CONCEPT OF A PHYLUM
- Life forms as different as sea anemones, earthworms, crocodiles and humans
are all classified as members of the animal kingdom.
- This is because they all contain EUKARYOTIC cells and have no cell walls.
- They are all multicellular and HETEROTROPHIC.
- Despite these similarities it is obvious that animal have diverse body plans.
- Animals that have the same body plan are placed in the same taxonomic group
or phylum.
, - Four key body plans are identified:
• Symmetry and cephalisation
• Number of tissue layers that develop from the embryo
• Number of openings in the gut
• Body cavity: coelom and blood system
SYMMETRY AND CEPHALISATION
- Body symmetry: refers to the arrangement of body parts around a central
point or plane.
- Cephalisation: refers to the tendency for the major sense organs, mouth and
brain to be grouped together at the front end (ANTERIOR) of the body.
- Animals with no symmetry are said to be asymmetrical. These animals lead a
sessile (stationary) life and are not capable of locomotion.
- Radial symmetry: is where the body can be divided into two equal halves
through more than one plane passing through a central axis of the body. This
type of symmetry enables locomotion in any direction and the animal can
respond to stimuli from all directions.
- In Bilateral symmetry: only a single plane passes through the centre of the
body dividing the animal into two equal halves. The animal has a definite
head and a definite tail end.
TISSUE LAYERS DEVELOPED FROM THE EMBRYO
- The different tissues that make up our bodies are all derived from special
tissue layers that form in the embryo.
The Scientific method
HYPOTHESIS TESTING
● WHAT IS A HYPOTHESIS?
- An attempt to explain some event or observation using whatever information
is currently available.
- It is a testable statement that may be supported OR not supported.
- Must: Have two variables (dependent and independent variables);
- State the relationship between the two variables;
- State the independent variable first (cause) and then the dependent variable
(effect).
- A hypothesis DOES NOT have to be a correct explanation of the
event/observation.
● Your DEPENDENT and INDEPENDENT variables should be IDENTIFIED
from the AIM OF THE INVESTIGATION AND...... your CONCLUSION
should ALSO be identified from the AIM of the identification.........
● INDEPENDENT VARIABLE
- Refers to the factor that is being investigated.
- This factor is usually manipulated / changed by the investigator either at the
start of or during the course of the investigation.
- The investigator decides what to test.
- The independent variable appears on the X-axis of a graph.
- Which factor did we CHANGE?
● DEPENDENT VARIABLE?
- Refers to the effect of the independent variable.
- This effect is usually measured or observed in some way and appears on the
Y-axis of a graph
- The results investigator is waiting for.
- Which factors did we MEASURE?
● CONSTANT/FIXED variables
- Which factors did we keep THE SAME?
● VALIDITY
- Validity questions show how the experiment/investigation was carried out.
, - It is important to be sure that all the factors/variables have been
controlled/fixed EXCEPT THE VARIABLE/FACTOR BEING TESTED.
- In questions which require learners to suggest some factors that might have
decreased the validity of an investigation, the answers should centre on the
criticism of the scientific process; for example, some factors/variables that
were not fixed/controlled when carrying out the investigation.
- FIXED VARIABLES LEAD TO VALIDITY
● RELIABILITY
- Repeat the investigation,
- Increase the sample size,
- Take many readings and use average, Select a random sample,increase the
period of the investigation.
● GRAPHS
- Heading
- y-axis = dependent variable
- x-axis = independent variable
- scale
- type of graph = line, bar, histogram, circle
- plot of data
● TABLES
- Heading
- Left column = independent variable
- Right column = dependent variable must have lines corresponding data must
be in line measuring units !!!
BIODIVERSITY IN ANIMALS:
THE CONCEPT OF A PHYLUM
- Life forms as different as sea anemones, earthworms, crocodiles and humans
are all classified as members of the animal kingdom.
- This is because they all contain EUKARYOTIC cells and have no cell walls.
- They are all multicellular and HETEROTROPHIC.
- Despite these similarities it is obvious that animal have diverse body plans.
- Animals that have the same body plan are placed in the same taxonomic group
or phylum.
, - Four key body plans are identified:
• Symmetry and cephalisation
• Number of tissue layers that develop from the embryo
• Number of openings in the gut
• Body cavity: coelom and blood system
SYMMETRY AND CEPHALISATION
- Body symmetry: refers to the arrangement of body parts around a central
point or plane.
- Cephalisation: refers to the tendency for the major sense organs, mouth and
brain to be grouped together at the front end (ANTERIOR) of the body.
- Animals with no symmetry are said to be asymmetrical. These animals lead a
sessile (stationary) life and are not capable of locomotion.
- Radial symmetry: is where the body can be divided into two equal halves
through more than one plane passing through a central axis of the body. This
type of symmetry enables locomotion in any direction and the animal can
respond to stimuli from all directions.
- In Bilateral symmetry: only a single plane passes through the centre of the
body dividing the animal into two equal halves. The animal has a definite
head and a definite tail end.
TISSUE LAYERS DEVELOPED FROM THE EMBRYO
- The different tissues that make up our bodies are all derived from special
tissue layers that form in the embryo.
