Year 9 Biology

Ecology

The scientific study of interactions between organisms and their environments, focusing on energy transfer. Therefore it is a science of relationships.

Biosphere

Life supporting portions of Earth composed of air, land, fresh water, and salt water

Ecosystem

Living organisms interacting with their physical environment, functioning as a unit

Community

All the living organisms (different species of plants and animals) in an ecosystem at a particular time)

Population

The number of organisms of one species living in an ecosystem at any given time. Eg: Number of clownfish in the reef

Organism

Any unicellular or multicellular form exhibiting all of the characteristics of life, an individual

Biodiversity

Number of different species, variety within species, vital for healthy sustainable ecosystem

Habitat

The place where an organism lives. Eg: A snail in the pond scum of a little pond

Competition

Competition occurs between organisms for food, shelter, mates and survival

Predator

An organisms that hunts, kills and consumes another organism (a prey) for energy

Prey

An organism that is hunted, killed and consumed by another organism (a preydator) for energy

Mutualism

A symbiotic relationship that benefits both species. Eg: Shrimp remove parasites form larger fish

Parasitism

A symbiotic relationship where one species benefits (parasite) and the other is harmed (host). Eg: Ticks

Commensalism

A symbiotic relationship where one species benefits and the other is neither harmed nor helped. Eg: Orchids growing on a tree

Bio Hierarchy

1. Biosphere

2. Ecosystem

3. Community

4. Population

5. Organism

Biotic

Definition: All living or once-living organisms in an ecosystem.

Examples: Plants, animals, fungi, bacteria, and even dead organic matter like fallen leaves.

Role: They directly and indirectly influence other organisms through interactions like predation, competition, and decomposition.

Abiotic

Definition: All the non-living physical and chemical elements in an ecosystem.

Examples: Sunlight, water, temperature, air, soil, and minerals.

Role: They are crucial for the survival of living things and can limit the growth and diversity of populations.

Symbiosis

The relationship between two organisms or different species that benefits one or both organisms

The three types of symbiosis

1. Mutualism

2. Commensalism

3. Parasitism

Photosynthesis

Plants making their own food using the energy from sunlight

Producers (autotrophs)

Organisms that make their own food

Consumers (heterotrophs)

Organisms that rely on other organisms for energy and nutrients

Decomposers

Organisms that break down the dead remains of other organisms (dead or decaying) such as plants or animals into simpler molecules that can be absorbed

Feeding relationships

1. Producer - Consumer

2. Predator - Prey

3. Parasite - Host

Food Chain

A simple model that shows how matter and energy move through the different trophic levels of an ecosystem

Food Web

Show all of the possible feeding relationships in a community at each trophic level. It represents a network of interconnected food chains.

Trophic Levels

Each link in a food chain is known as a trophic level. Trophic levels represent a feeding step in the transfer of energy and matter in an ecosystem.

Energy

The amount of fuel that an organism represents to its predators or consumer measured in joules.

- As you move up a food chain the available energy decrease

- Energy is transferred upwards but is diminished with each transfer due to the energy used by the organism in the process of living

-Energy enters ecosystems as light energy from the sun. It passes along the food chain as chemical energy

- About 10% of energy available at one level is transferred to the next level

- For example, if producers have 100% energy, primary consumers will have 10% and secondary 1%

Pyramids of energy

- Some energy is also wasted because consumers cannot digest all the food that they eat

- Because energy is lost in a food chain, energy is converted to biomass (the mass of plant and animal tissue) declines as each level, limiting the length of food chains

Pyramids of Biomass

Biomass is the amount of organic matter comprising a group of organisms in a habitat measured in kilograms.

•As you move up a food chain available biomass decreases.

•To sustain a kilogram of top predator requires many kilograms of prey.

•To sustain many kilograms of herbivores requires a very large mass of producer (grasses).

Productivity

Productivity is the rate at which living tissue can be produced by the ecosystem.

•The productivity of a field of grass can be described as adding kilograms per day.

•The productivity of beef cattle can also be described in terms of how many kilograms per day are being added.

Pyramids of Number

Number is the amount of organisms in a habitat.

•As you move up a food chain generally the number decreases.

•However, one large producer may be capable of supporting many consumers.

Above the second trophic level the pyramid of number usually decreases

Bushfires

A bushfire is an unplanned vegetation fire. It is a generic term that includes grass fires, forest fires and scrub fires.

Causes of bushfires

Bushfires are caused by both natural ignition sources like lightning and human activities, including accidental and deliberate acts. Key factors like dry vegetation, high temperatures, and strong winds create conditions that allow fires to start and spread rapidly.

Plant regeneration after Bushfires

Plant regeneration after a bushfire occurs through several mechanisms, including resprouting from protected buds and germinating from seeds stored in the soil or released by the fire. Common examples include eucalypts using epicormic shoots, grasstrees resprouting from a protected apical bud, and banksias whose cones open to release seeds after a fire.

Droughts

Long periods of unusually low precipitation

What do plants need to grow and survive

- healthy soil that provides water and minerals

- CO2 and water, with sunlight to photosynthesise and produce

glucose and O2 - oxygen.

- Root hairs increase the surface area of the roots for efficient

absorption of water (by osmosis) and minerals from the soil

Plants in hot arid habitats

- Reflect extreme sunlight

- Store and conserve water

- Defend against increased predation

Plants in cold low precipitation habitats

-Avoid or tolerate freezing

- Shallow root systems

- Potent flowers to attract pollinators

Osmosis/Diffusion

Diffusion is the general movement of any substance from a high to a low concentration area, while osmosis is a specific type of diffusion where only water molecules move across a semipermeable membrane from a high to a low water concentration

Active Transport

- Carrier molecules pump soil minerals into plants

- Process requires energy

Loss of Biodiversity

- Clearing of native vegetation

- Introduced plants and diseases

- Poaching and illegal trade in wildlife

- Pollution of species or habitats

Nervous System

The network of nerve cells and fibres that transmits nerve impulses between parts of the body.

Motor Neuron

The nerve cell that transmits impulses from the brain or spinal cord to a muscle or gland

Sensory Neuron

The nerve cell that carries impulses from a sense receptor to the brain or spinal cord

Relay Neuron

The nerve cell that connects sensory and motor neurons

Labelled Neuron

Nucleus

Contains DNA of the cell and is generally in the centre

Cell body

In charge of the neuron's activities

Axon

Sends messages from the cell body to the dendrites of other neurons

Axon Terminal

Sends messages to other neurons (across the synapse)

Dendrites

Receives messages from other neurons

Myelin Sheath

Covers the axon to protect it and help messages travel faster and easier

Schwann cell

A Schwann cell is a type of glial cell in the peripheral nervous system that forms the myelin sheath, an insulating layer that speeds up nerve impulses. These cells also provide support and nutrients to axons and are crucial for nerve development and repair.

Nodes of Ranvier

Gaps in the myelin sheath to which voltage-gated sodium channels are confined.

Muscle Fibres

Cells that contract to produce movement.

Neurotransmitters

Chemicals released in the synapse

Synapse

A junction where information is transmitted from one neuron to the next.

Spinal Reflexes

Simple pathways in the nervous system that rapidly generate muscle contractions

Spinal Reflex Example

- Heat stimulus from iron

- Pain receptor in fingers senses high temperature

- Sensory neuron carries impulse to spinal cord

- Relay neuron connects sensory neuron to motor neuron in spinal cord

- Motor neuron carries impulse to to muscle

- Muscle contracts

- Hand moves away from heat

The Pupil Reflex

Reflex contraction of the muscles of the iris in response to a bright light causing the pupil to become smaller.

Goitre

An abnormal enlargement of the thyroid gland located at the base of the neck

What gland and hormone is involved with Goitres

The thyroid gland, which enlarges due to various reasons and its function can be affected by thyroid hormones and thyroid stimulating hormones from the pituitary gland.

Causes of a goitre

- Grave's disease (hyperthyroidism)

- Toxic multinodular goitre (hyperthyroidism)

- Hashimoto's thyroiditis (hypothyroidism)

- Iodine deficiency

Factors increasing the risk of a goitre

- Being female

- Over 40

- Family history of a thyriod diseases

- Radiation exposure to the neck or chest

Symptoms of a goitre

-enlarged thyroid

-due to underactive thyroid or lack of iodine in diet

-appears as a lump or "bubble" on the neck

Diagnose and treatment for a goitre

Diagnose:

- Physical exam

- Blood tests

Treatment:

- Surgery

Chemical equation for Cellular Respiration

C6H12O6 + 6O2 --> 6CO2 + 6H2O + ATP

How does oxygen get to the cells

You breathe in oxygen, then it travels through the bronchial tubes and alveoli in your lungs. Then it gets pumped to your heart, where it gets pumped all around your body.

How does glucose get to the cells

Absorbed in small intestine into bloodstream, blood delivers glucose to cells

How is carbon dioxide removed from the body

It is removed through the lungs when we breathe out

Cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Homeostasis

•The maintenance of a relatively constant internal environment despite fluctuations in the external environment.

•A stable environment allows the body to function efficiently.

•To maintain homeostasis the body must be able to sense changes in the internal and external environment and compensate for these changes

•A feedback system is a way in which the body responds to a change (or stimulus) with the response altering the original stimulus

Stimulus Response model

Homeostasis uses the stimulus response model to keep the internal environment stable (within defined limits).

The stimulus response model has 5 components

Stimulus

The change in the environment

Receptor

Detects the change in the environment. A nerve then sends a nerve impulse to the modulator/control centre

Modulator

The part of the body that decides on the response.(control centre) This part sends messages (neural & hormonal) to the effectors

Effector

The part of the body that carries out the repsonse

Response

The desired action

Negative feedback

When the response is opposite to the stimulus

Ectotherms

An animals that warms itself mainly by absorbing heat from its surroundings and so do not need to eat often/much. However, they are only active when they are warm / summer.

Endotherms

Humans are endotherms. We produce most of our heat using cellular respiration and so we need to eat a lot/often. However, we can be active at any time of the day/season.

Thyroid

Controlled by the brain to make thyroxine

Thyroxine

Controls the rate of cellular respiration in cells (metabolism) and therefore heat production.

How heat is gained

•Heat lost in respiration from all cells in the body.

•Heat released from respiration in muscle cells during exercise.

•Absorbing heat from the sun and environment on a hot day.

•Eating hot food and drinking hot drinks.

How heat is lost

•Radiating heat from the warm blood flowing in capillaries just beneath our skin.

•Evaporation of sweat from the skin cools the skin beneath.

•Heat lost in the warm breath we breathe out.

•Heat lost from warm urine and faeces expelled from the body.

Effects of Exercise

- Generate heat

- Brain detect a higher blood pressure

- Brain sends nerve impulses to the sweat glands

- The sweat glands are activated to reduce the temperature

Carbohydrates are...

Fully digested to glucose which is absorbed in the small intestine (by the villi)

Glucose

Blood contains glucose which is an important source of energy for the body (Cellular Respiration).

The glucose in blood must be kept within a normal range for the body to work properly.

If it rises or falls significantly, the body can usually bring it back to normal. This process maintains homeostasis.

Regulation of glucose by hormones

Hormones are chemical messengers produced in one part of the body and carried in the blood to cause some action in another part of the body. Different hormones have different actions.

The level of glucose is regulated by the hormones, insulin and glucagon, both released by the pancreas.

The pancreas ...

Detects the changes in blood glucose concentration and releases the appropriate hormone

Pancreatic cells

Alpha cells produce glucagon.

Beta cells produce insulin.

Insulin

A protein hormone synthesized in the pancreas that regulates blood sugar levels by facilitating the uptake of glucose into tissues

Excretory system

The system that removes waste from your body and controls water balance

Kidney

Organ that removes urea, excess water, and other waste products from the blood and passes them to the ureter

Bladder

Elastic, hollow, muscular organ that provides temporary storage for urine.

Cortex

Outer layer of the kidney

Medulla

To concentrate urine and regulate water and salt balance in the body

Pelvis (renal pelvis)

Large, funnel-shaped area within each kidney. It collects urine from the major calices and then narrows to become the ureter.

Ureter(s)

The tubes that carry urine from the kidneys to the bladder.