INTRODUCTION TO BIOLOGY
Characteristics of Life
The characteristics of life are those activities and characteristics that are unique to living organisms. These characteristics can help define a living organism from a non-living thing.
The 9 characteristics of life are:
1. Cells
2. Nutrition
3. Respiration
4. Excretion
5. Growth and Development
6. Movement
7. Reproduction
8. Sensitivity
9. Adaptability
Though these nine characteristics are unique to living things, they may be characteristic to non-living things as well. Hence the two most important characteristics which only living things possess are growth and development; and reproduction.
Biological System of Classification
Q. A non living thing such as a bicycle does not grow. However, a crystal immersed in a saturated solution may increase in size. How is this change different from that of a living organism?
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A. In living organisms, the growth is permanent, and is usually due to an increase in cells. The crystal does not contain cells, and the change in size is due to a chemical process which can also be reversed using other chemical processes.
Cells - The smallest unit of life capable of living in an environment free of life.
Nutrition - Process by which organisms take in food and convert it into new protoplasm (living matter).
Respiration - The oxidation of food substances to release energy for cell activities.
Excretion - Removal of metabolic waste products from organism
Locomotion - Ability to move from one place to another
Adaptation - Characteristics of an organism that improves its chances of surviving in its environment.
Reproduction - Biological process by which new individual organisms - offspring - are produced from their parents.
Classification - Group living organisms according to their similarities and differences.
To make the classification of animals easier and more systematic, the biological system of classification was created which groups animals according to different groups (traits they possess). As one goes down the order of classification similarities between different species increase. The diagram is shown on the right.
Binominal System - Created by Carlous Linnaeus, Latin is used to give two names to each species. The first name refers to the genus (always starts with a capital letter), and the second name refers to the name of the species (always starts with a small letter).
E.g.
Genus Species
Felis domestica (Domestic Cat)
Panthera tigris (Tiger)
Panthera leo (Lion)
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Through this it can be seen that the tiger and lion are different species but come from the same genus. The lion and tiger belong to the same family of the domestic cat, 'felidae'.
Kingdom
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Phylum
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Class
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Order
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Family
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Genus
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Species
Types of Microscopes
Light Microscope: 1000 x magnification (compound microscope is same principle, but can be used indoors, direct source of sunlight is not required)
Electron Microscope: More than 200 000 x magnification)
*Micro-graphs are images created by microscopes
*Micro-graphs created by light microscopes are colored, but micro-graphs made by electron microscopes are black and white and can be artificially colored.
EUKARYOTES PROKARYOTES
(True nucleus) (Before nucleus)
DNA inside nucleus No nucleus, naked DNA
Cells & Organelles
Cell Surface Membrane
- Selectively permeable membrane which regulates entry and exit from the cell
- Composed of lipids (fats)
- Every organelle other than ribosomes have a cell membrane (similar to the cell surface membrane)
Cytoplasm
- A medium for all chemical activities inside a cell
- Nutrients ( waste --> cytoplasm; used up --> vacuole; energy --> mitochondria)
- All organelles are present inside the cytoplasm
Nucleus
- Chromatin condenses into chromosomes during replication of cell
- Chromatin stores DNA (Deoxyribonucleic acid)
- Nucleolus makes ribosomes of the cell. The nucleolus contains protein.
Figure 1 Animal Cell Cytoplasm & Cell Membrane
Figure 2. Nucleus
Cell Wall
- Made of cellulose
- Only present in plant cells
- Provides protection and gives cell a fixed shape
- Allows turgidity in water
Rough Endoplasmic Reticulum (R.E.R)
- Flattened structure attached with ribosomes (Ribosomes give the R.E.R a rough texture/look
- Joined to the nuclear envelope
- Synthesizes protein and modifies them
Ribosomes
- Small, globular structures
- Do not have membrane; protein in nature
- Made in nucleolus
* Lying freely - Protein for use inside the cell
*Attached to the ER - Protein for use outside the cell (sent to Golgi Apparatus by ER)
Smooth Endoplasmic Reticulum (S.E.R)
- Tubular
- No ribosomes attached
- Synthesizes lipids and steroids (sex hormones)
- Detoxification of harmful material in SER
- Substances synthesized in the E.R (endoplasmic reticulum) are sent to the Golgi apparatus to be chemically modified.
- DNA controls cell by making proteins synthesize
Golgi Apparatus
- Flattened disk like structures stacked onto one another
- Chemically modifies substances made by the ER (lipids, steroids, proteins)
- Processes and packages substances in membrane (vesicle) for secretion outside of the cell
Vesicles: Lysosomes
- Lysosomes are a type of vesicle which have enzymes inside them and digest harmful material inside a cell
-All membranes inside the cell are similar to allow the easier integration of substances from one organelle to another (as can be seen with the ER and Golgi Apparatus)
Mitochondria
- Powerhouse of the cell
- Sausage shaped
- Double membrane
- Makes energy for cell
- Cellular respiration takes place in mitochondria
*Contains ATP (Adenosine tri phosphate) ​
Chloroplast
- Double membrane
- Contains chlorophyll (green pigment)
- Chlorophyll is essential for photosynthesis
Vacuole
- A fluid filled space surrounded by membrane (called tonoplast)
- Stores substances for usage later on
Plant: Permanent large vacuole
Animal: Temporary small vacuoles
Figure 3. Cell Wall in Plant Cell
Figure 4. Endoplasmic Reticulum
Figure 5. Movement of Substances from Golgi Apparatus to outside cell
Figure 6. Mitochondria
Figure 7. Chloroplast
Figure 8. Vacuole in a Plant Cell
Centrioles
- Small oval structures
- Appear in pairs
- Found near the nucleus
- Helps in cell division
- Found in only animal cells
Difference between Animal and Plant Cell
Plant Cells
- Large Permanent Vacuole
- Cell Wall
- Chloroplast
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Animal Cells
- Multiple small temporary vacuoles
- Centrioles
Figure 8. Difference between animal (left) and plant (right) cell
Specialized Cells
There are 50 - 75 trillion cells present in the body, of which there are 220 types of specialized cells.
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Specialized cells carry out different functions; they have different shapes, sizes, and features according to the function of the cell. Stem cells become into specialized cells through cell differentiation.
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Stem Cells
- Do not have a 'specific' function
- Reproduce quickly and have all organelles
- Become specialized through cell differentiation
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Red Blood Cells (RBCs)
- Contain haemoglobin (contains iron - binds to oxygen)
- Oxygen transported around the body
- No nucleus (more area for haemoglobin)
- Increased surface area to volume ration (SA:V)
- Made in bone marrow
- Cannot divide and replicate once specialized
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Root Hair Cells
- Long and narrow --> SA:V
- Water and minerals obtained through diffusion
- Found only in plants
- Does not contain chlorophyll
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Xylem Vessels
- Long hollow tubes from root to leaves
- Narrow and no cross walls in lumen
- Don't have protoplasm
- Walls thickened with lignin for support
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Nerve Cells
- High Potassium to Calcium Gradient
- Long 'arms' to cover greater distance
- Sends electrical impulses to and from the brain to the body.
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Cilia
- Tiny hair like extensions
- Found in trachea and in ears
- In ear, cilia helps to discern the 'pitch' of sound
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Trachea Cilia
- Helps keep dirt out of lungs
- Secrets mucus
- These extensions use muscles to move dirt away from lungs to the mouth
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Muscle Cells
- Contracts and Expands
- Mitochondria uses ATP (Adenine tri-phosphate) to produce energy when muscles contract
- Too much of chemicals can make muscles forget to relax (resulting in muscle spasms)
Cells
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Tissues (Simple/Complex)
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Organ
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Organ System
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Organism