Science Year 9 Semester 1 (The Nervous System (3.5 Things can go wrong…
Science Year 9 Semester 1
2.1: All living things are dependent on each other and the environment around them.
An ecosystem is a community of biotic (Living) factor and their abiotic (Non-Living) surroundings.
As small as a puddle or as large as the earth
Plants and animals constantly cycle gases. For example, plants take in carbon dioxide and release oxygen, which the animals breath in and release carbon dioxide.
Many organisms living together in the same environment because they find their requirements there.
A population is a group of organisms of the same species living in the same place at the same time. When they interact with each other they are called a community.
A biosphere describes the living world
Intersection between land, gases and water aka the lithosphere, atmosphere and hydrosphere.
Study it in small sections called ecosystems
Must supply all needs of organisms so they will want to live there, such as food, water, oxygen, warm temperature, ect, ect.
2.2: Relationships between organisms
Relationships within a species
Collaboration: Where organisms work together to ensure mutual survival.
Mating: When two members of the same species produce offspring
Competition: When organisms of the same species compete for food, mating partners, territory ect ect.
Relationships between different species
Mutualism: A relationship where both organisms benefit
Commensalism: A relationship where one organism benefits and the other is unaffected (Rare)
Parasitism: A relationship that is beneficial to one organism but is detrimental to the other.
Predator-Prey: A relationship where one organism hunts and kills the other for food
Competition: A relationship where two organisms of different species compete for food
Inhibition is a specific type of competition where one organism produces a chemical that deliberately inhibits the growth of the other.
2.3 Population depends on biotic and abiotic factors
Death and emigration must equal birth and immigration
If one thing on a food web alters, it effects the whole ecosystem
Example food web:
Changes in the ecosystem upset the balance, but a new balance becomes normal and it bounces back.
Examples of changes in the ecosystem:
The study of changes in population numbers within ecosystems
Scientists can only estimate and they do this by using a formula for moving creatures
N1 = The first capture they make. They tag these ones and release them
N2 = The total number in the second capture
M1 = the tagged ones in the second capture
Formula for estimate of the population: (N1 x N2) / M1 or in words N1 times N2 divided by M1.
For stationary organisms, scientists use quadrats, which are 1m by 1m squares that they hold over a few sections of land with these organisms on it, then they take photos and count the organisms in each, average it out and times it by how many square metres the area is. They then have an approximation of how many stationary organisms of that type there are in that area.
2.4 Introducing a new species can upset the balance of the ecosystem
The Nervous System
3.1 Receptors detect stimuli
Stimuli are any signal your body picks up that prompts a response
An example would be when you touch a hot plate and your hand instinctively jerks back. That is the receptors in your skin detecting the heat which is damaging to the body and protecting you from it.
The structures that receive stimuli
The sense organs
5 main senses
The pupils change size depending on how much light enters the eye. The light becomes nerve signals for your brain and your brain transforms it into a image.
There are receptors in your nose that detect particles in the air, and they send the information to the brain which interprets it and tells you what you are smelling.
Your ears pick up on vibrations; for example from the strumming of a guitar. The vibrations are converted into nerve impulses and sent to the brain, which interprets what you are hearing.
You taste with your taste buds, which are small receptor cells that detect the chemicals in food. This information is sent to the brain which tells you what you are tasting
Touch is felt through nerve receptors in the skin and is processed by the brain.
5 main sense organs
3.2 Nerve cells are called neurons
Scientists believe we could have 100 billion neurons in out bodies
Neurons look like this:
Dendrites receive information, which is processed by the nucleus and then sent to the next neuron by the axon terminals.
The axon can also be called a nerve fibre
When the messages are decoded, the axon releases a neurotransmitter to move to the next dendrite, and the process repeats.
Different types of neurons include:
Sensory Neurons that collect information from the outside world and send it to the brain
Motor Neurons carry signals to tell your muscles to move
Connector neurons connect sensory and motor neurons as well as other connector neurons.
The Myelin sheath is the space between two neurons where the neurotransmitter travels
3.3 The nervous system provides fast control of the body
Stimulus response model
Reflexes are automatic responses that happen before the message even reaches the brain when quick action is required.
Knee jerk reflex
3.4 The central nervous system receives information from the peripheral nervous system
Central nervous system (CNS)
Perception of senses
Recognition of sounds and smells
Responsible for various aspects of vision
Processes all messages from the PNS
Peripheral nervous system (PNS)
Somatic nervous system
Responsible for voluntary muscle movements
Automatic nervous system
Responsible for involuntary actions
Maintains your bodies inner environment (Homeostasis)
Has two parts
Sympathetic division (Speeds up heart rate when necessary)
Parasympathetic (Slows down your heart rate)
3.5 Things can go wrong with the nervous system
If a disc in your vertebrae slips, it is very painful
Usually treatment is pain relief and occasionally an operation to remove the disc
This happens when the myelin sheath becomes damaged
Messages can't pass through
Messages from below the injury to the brain are blocked, which means you can't move anything below the injury
in some cases you can still use your arms, in others that is not the case
Motor neuron disease
Causes the motor neurons to become weaker and eventually stop working.
Progressive damage to neurons in the brain
Causes loss of short and long term memory and eventually death
3.6 The endocrine system
The endocrine system is a collection of glands that release hormones
Full table of hormones, target cells, glands and purpose
Some cells in the body are target cells, which receive hormones. It only takes one hormone to make a change in the target cell
Made from proteins
Travel through the bloodstream until they reach their target cell
Made from cholestrol
Includes those excreted from the ovaries and testes
Prepares body for flight or fight
3.7 Homeostasis regulates through negative feedback
To maintain homeostasis (the state of normal operation in your body) your body responds to stimuli from the sense organs and acts accordingly by sending messages to effectors around your body. Efffectors are glands and muscles that cause a change in the way your body functions
For example, if it gets hot your body tries to cool you down by sweating.
Hormones at work
Regulated by negative feedback mechanism
If something is too much the response is to send a hormone to remove it
If glucose levels are really high, insulin is released to counteract
If they are too low, glucagon is released and it binds to spare glucose and levels are restored
You get glucose from eating