AGF SciencePot: 2010

Wednesday, November 17, 2010

Ecological Relationships

What Is Ecology?
Ecology is about the pattern of nature.
It is the study of the interactions among living organisms and their environment.

Every living thing depends on other things for survival.

What Is a Habitat?
A habitat is a place where an organism lives, and it provides the organism with the essentials of life so that it can carry out all the seven life processes.

A habitat provides animals with food, shelter and water
A habitat provides plants with light, water and a place to grow

Different habitats have different environmental condition such as temperature and amount of water.

the habitat of a plant or animal must provide all the things that it needs to live and reproduce.

Different plants and animals have different needs. For example a gerbil can survive on less water than a mouse. This is because it has the features that help it to survive. We say that it is adapted to its environment.

Classifying animals
When we put plants and animals into groups we say that we classify them.

Animals with backbones are called vertebrates
Animals without backbones are called invertebrates

Examples of Vertebrates

Mammals are a class of vertebrate, air-breathing animals whose females are characterized by the possession of mammary glands while both males and females are characterized by hair and/or fur

Reptiles are characterized by laying shelled eggs and having skin covered in scales. Reptiles are classically viewed as having a "cold-blooded" metabolism.

Birds are winged, warm-blooded, egg-laying, vertebrate animals.

Amphibians ( from Amphi- meaning "on both sides" and -bios meaning "life"), such as frogs, salamanders, and caecilians, are cold-blooded animals that develop from a juvenile water-breathing form, either to an adult air-breathing form, or retains some juvenile characteristics.

Fish is any aquatic vertebrate animal that is covered with scales, and equipped with two sets of paired fins and several unpaired fins. Most fish are "cold-blooded"

Examples of Invertebrates

Mollusc

Annelids

Flatworms

Arthropods

Coelenterates

Now let's classify green plants
There are hundreds of thousand of different plants, so we didide them into smaller groups to help us to identify and to study them.
There is more than one way of doing this.

Some plants have a special transport system for food and water called a vascular system. So we call these plants vascular plants.

Plants without a vascular system are called non-vascular plants.

Questions

What is the meaning of the word habitat?
Explain why organisms are adapted to their environment

Cells

Animals and plants are made of cells. Cells form the basic "building blocks" for living things. Some cells have specialised functions.
Tissues are made from cells of a similar type. Organs are made from tissues, and systems are made from several organs working together.

Cells are very small. They are the basic building blocks of all animals and plants. These photographs show cells seen through a microscope.

Cheek cells

These are cheek cells, seen through a microscope:

Onion cells

These are onion cells, seen through a microscope:

Animal cells usually have an irregular shape, and plant cells usually have a regular shape
Cells are made up of different parts. It is easier to explain what these parts are by using diagrams like the ones below.

Animal and plant cells both have a cell membrane, cytoplasm, and a nucleus. Plant cells also have chloroplasts, a vacuole and a cell wall.

Animal cells and plant cells both contain:

cell membrane, cytoplasm, nucleus

Plant cells also contain these parts, not found in animal cells:

chloroplasts, vacuole, cell wall

The table summarises the functions of these parts.

Part	Function	Found in
Cell membrane	Controls what substances can get into and out of the cell.	Plant and animal cells
Cytoplasm	Jelly-like substance, where chemical reactions happen. In plant cells there's a thin lining, whereas in animal cells most of the cell is cytoplasm.	Plant and animal cells
Nucleus	Controls what happens inside the cell. Carries genetic information. In exams don't call the nucleus the 'brain' of the cell. That is not a good description and will not get you marks.	Plant and animal cells
Chloroplast	Where photosynthesis happens – chloroplasts contain a green substance called chlorophyll.	Plant cells only
Vacuole	Contains a liquid called cell sap, which keeps the cell firm.	Plant cells only
Cell wall	Made of a tough substance called cellulose, which supports the cell.	Plant cells only

Humans are multi-cellular animals. That means we are made of lots of cells, not just one cell. The cells in many multi-cellular animals and plants are specialised, so that they can share out the processes of life. They work together like a team to support the different processes in an organism.

Specialised cells

You should be able to work out special features of a cell from a drawing, if you are told what the cell can do. The tables below show examples of some specialised animal and plant cells, with their functions and special features.

Type of animal cell	Function	Special features
Red blood cells	To carry oxygen	Large surface area, for oxygen to pass through Contains haemoglobin, which joins with oxygen
Nerve cells	To carry nerve impulses to different parts of the body	Long Connections at each end Can carry electrical signals
Female reproductive cell (egg cell)	To join with male cell, and then to provide food for the new cell that's been formed	Large Contains lots of cytoplasm
Male reproductive cell (sperm cell)	To reach female cell, and join with it	Long tail for swimming Head for getting into the female cell

Type of plant cell	Function	Special features
Root hair cell	To absorb water and minerals	Large surface area
Leaf cell	To absorb sunlight for photosynthesis	Large surface area Lots of chloroplasts

Tissues

Animal cells and plant cells can form tissues, like muscle tissue. A living tissue is made from a group of cells with a similar structure and function, which all work together to do a particular job. Here are some examples of tissues:

muscle
the lining of the intestine
the lining of the lungs
phloem (tubes that carry dissolved sugar around a plant)
root hair tissue (for plants to take up water and minerals from the soil)

Organs

An organ is made from a group of different tissues, which all work together to do a particular job. Here are some examples of organs:

heart
lung
stomach
brain
leaf
root

Organ systems

An organ system is made from a group of different organs, which all work together to do a particular job. Here are some examples of organ systems:

circulatory system
respiratory system
digestive system
nervous system
reproductive system
leaf canopy

click here to try some questions

source:
http://www.bbc.co.uk/apps/ifl/schools/ks3bitesize/science/quizengine?quiz=cells&templateStyle=science

Monday, November 15, 2010

Microbes & Diseases II

Protecting ourselves against diseases

Your body has several ways defends itself against micro-organisms.

· Sweat and tears contain an enzyme that kills bacteria.

· Hairs in your nostrils trap micro-organisms and mucus contains enzymes that can kill bacteria.

· Enzymes in saliva can kill bacteria.

· Most bacteria swallowed with food and drinks are killed by acid in the stomach.

But microbes get past these defenses

Tuberculosis (TB) is a serious disease that destroys lung tissue.

TB comes with a bad cough and each time a person with TB cough, they spray little droplets into the air. These droplets contain TB bacteria.

If you are nearby, you can breathe them in.

What happens when you catch a cold

Several different viruses cause colds. When you have a cold and sneeze, you spray several droplets of liquid into the air. Each droplet contains thousands of viruses.

When you first catch a cold, the virus multiplies very quickly. You begin to feel ill, with a runny nose, sore throat and a cough.

Your body starts to fight back the invasion; cold viruses are destroyed and you start to feel better.

How your body destroys microbes

Your blood contains red blood cells and white blood cells. There are two different types of white blood cells.

1. One type of white blood cell engulfs (traps) microbes and destroys them.

2. Another type of white blood cell makes disease-fighting substances called antibodies. These can stop microbes from causing disease.

Each antibody that you make is specific to fighting one type of microbe.

An antibody won’t work against any other type of microbe.

Different microbes need different antibodies. It takes time for your body to make these different antibodies, and you feel ill until you have enough antibodies to destroy the microbes.

Once you have had a disease, your white blood cells have learnt how to make the antibodies. They will be able to make the right ones much more quickly in the future.

If a second attach comes, your body can destroy the microbes before they have time to make you ill. This means you are immune to the disease. You have immunity.

Active immunity

This happens when people make their own antibodies to a disease.

Natural: if you have been infected with a disease, your body made antibodies to destroy it. Your body remembers the disease, and is ready to make antibodies quickly if you were ever infected again.

Artificial: you can be injected with a vaccine containing weakened or dead microbes, or some bits of microbes. The active live microbes are not present, so the vaccine does not make you ill. But your body reacts to the microbes and sets about making antibodies to fight them. It then remembers how to make these antibodies, ready to react if you are ever infected with the disease.

Passive immunity

With passive immunity, people are given ready-made antibodies.

Natural: pregnant women pass on their antibodies to their growing baby through the placenta.

There are also antibodies in breast milk. This gives newborn babies some immunity from microbial infections.

Artificial: antibodies are made outside the body, for example in the laboratory. These antibodies are injected into people and animals to give protection from fast-acting microbes. An example is the anti-tetanus vaccine. You may be injected with this if you have a deep or dirty wound where tetanus bacteria may grow. Your body may not make its own antibodies fast enough to fight.