TOPIC 6: Organisms Respond to Changes in their Environments

Taxis

A directional movement of an organism in response to a stimulus.

Kinesis

A non-directional movement of an organism in response to a stimulus.

Tropism (Positive & Negative)

Growth response of a plant to a directional stimulus.

Positive is towards a stimulus and Negative is away from a stimulus.

Auxins

Plant hormones promoting growth.

Indoleatic Acid (IAA)

An auxin, produced in the tips of shoots in flowering plants.

Null Hypothesis

Hypothesis stating there is no difference between the factors being investigated.

Chi-Squared

Statistical test where you compare the expected result and the observed result.

Correlation Coefficient

Statistical test where you draw a line of best fit on a graph.

Standard Deviation

Statistical test using a bar chart and error bars to measure deviation from the mean.

T-Test

Statistical test where you compare the results of 2 sets of data.

Sodium Ions (Na+)

Move into the neuron during depolarisation..

Potassium Ions (K+)

Move out of the neuron to repolarise the membrane.

Depolarisation

Process where a neuron's membrane potential becomes less negative, leading to an action potential.

Resolution

Ability to distinguish between 2 seperate points.

Habituation

Reduction of response when a specific stimulus occurs repeatedly.

Baroreceptors

Pressure-sensitive mechanoreceptors found in the walls of blood vessels that detect changes in blood pressure.

Chemoreceptors

Sensory receptors that detect changes in the blood's oxygen, carbon dioxide, and pH levels.

Myogenic Contraction

Muscle’s ability to contract and relax without recieving signals from nerves.