Introduction to Biology - Basic Characteristics of Life

len Alfred Ajibola - Wed, 23rd January, 2019 @ 02:32:52 AM

Topics in Biology

Male Reproductive System: External and Internal Male Genitals Male accessory sex organs Food Chain, Food Web and Food Pyramid Skeleton, Type of Skeletal Materials and Differences between Cartilages and Bones Bones - Types of Bone Bones and Type of Bone part 2 Red Blood Cells and Hemoglobin Tropical Rainforest and Savanna with their characteristics Desert and Swamp Forest - Types of Desert, Characteristics of Deserts and Swamps Plant Nutrition and Photosynthesis - Autotrophic mode of Nutrition Amazing facts in Biology Protists - Examples and Characteristics of Protists Reptiles - Characteristics of Reptiles Homeostasis and Negative Feedback Mechanism Arteries, Layers of an Artery and Characteristics of Arterial Disorders Introduction to Biology - Basic Characteristics of Life

Academic Questions in Biology

Please check out our Test Your Knowledge page to see all Questions and Answers

Which of the following is a category of long bones?

  • A. Stunted long bones
  • B. Reduced long bones
  • C. Giant long bones
  • D. Bended long bones
  • E. Curved long bones
  • F. Elongated long bones

The end product of photosynthesis is _____.

  • A. O2
  • B. C​​​​​​2​​​​C5OH
  • C. H2​​​​​O
  • D. CO2
  • E. C6H12O6
  • F. C2H5COOH

The above diagram illustrates a _____.

  • A. Food Chain
  • B. Food Web
  • C. Food Pyramid
  • D. Food Link
  • E. Food Hub
  • F. Food zone

The living cells that makes up cartilages are called _____.

  • A. osteocytes
  • B. osteoblasts
  • C. osteoclasts
  • D. chondroblasts
  • E. chrondocytes
  • F. Osteoprogenitor cells

Which of the following statement is incorrect with regards to chitin?

  • A. Ecdysis is a term associated with chitin
  • B. It is a skeletal material
  • C. It is a type of skeleton
  • D. It is present outside the organism
  • E. It does not grow when the organism grows
  • It is present in ants

Which of the following is NOT a function of the human skeleton?

  • A. Gives Shape
  • B. Provides Protection
  • C. Aids in Locomotion
  • D. Supports Movement
  • E. Assists in Inhalation and Exahalation
  • F. None of the above
  • G. All of the above

Organisms that manufacture their own food through the help of sunlight or chemicals are best referred to as _____.

  • A. autotrophs
  • B. chemosynthetic
  • C. photosynthentic
  • D. chemoautotrophs
  • E. photoautotrophs
  • F. chemoautotrophs

Organisms that begins a food chain and also manufacture their food through photosynthesis are best referred to as _____.

  • A. heterotrophs
  • B. autotrophs
  • C. homotrophs
  • D. producers
  • E. photosynthetic
  • F. chemosynthetic

What is Biology?

Biology is one of the core sciences taught and the senior level of secondary education; the others being physics and chemistry.

Science as we know is a systematic process of making enquiry about living and non-living things.

The word "Biology" originated from two Greek words. These are “Bios” and “Logos”. “

Bios” means life while “Logos” means knowledge or to study, hence:

Biology can be defined as the study of life.

This is why some people often refer to biology as a life science.

Note: Life goes beyond plants and animals; but basically, we can group biology into 2 main branches. These are

  • Botany
  • Zoology

Botany refers to the study of plants

zoology is simply the the study of animals.

In biology, anything that has life is generally referred to as a living organism.

Living organisms are found on every part of the earth; from the soil (lithosphere) to the waters (hydrosphere) and the air (atmosphere).

Please read on the Atmosphere here.

In many instances, we use the term organism to refer to living organism.

Some scientist are of the school of thought that a virus is not a living organism while others consider them to be living.

In reality, viruses are unusual group of organisms because outside a living cell, they possess no characteristics of life (as we shall discuss later); thus are considered inanimate and non-living (just like a stone or paper).

All living things are built on microscopic units called cells but viruses on the other hand do not have an ideal cell structure, thus cannot carry out life processes on their own.

Conversely, when they find themselves in a living organism (a cell or tissue), they become "living"; as they can now carry out some life activities like reproduction.

From the above reasons, Viruses are preferably considered to be in the borderline of life.

The majority of living organism cannot be seen with the naked eyes. For instance, it is reported that an average human being has an estimated 100 trillion micro-organisms within and around them. A microscope is needed to see them, thus are referred to as microscopic organisms or micro-organisms.

All microscopic organisms are single-celled or unicellular. Bacteria and Protists typically falls within this group of organisms.

Please read more on Protists here.

Consider studying Microbiology if you are really interested in microscopic organisms.

Please read on Micro-organisms causing Food, Air and Water Borne Diseases here.

Larger organisms have multiple cells, hence are termed multi-cellular organisms. For instance, Humans are composed of trillions of cell.

Note: All living organism will need certain non-living factors (Abiotic factors) within their environment for survival. For instance, living organisms require air and water (which are non-living components of their environment) to stay alive.


Characteristics of Living Organisms

There are certain characteristics that are used in determining whether something is living or not; for instance, a stone cannot move and this makes it non-living. The point is; every living organism must be able to move; thus movement is regarded as one of the basic characteristics of all living organism.

Below are the basic characteristics of living organisms

1. Movement: All living organisms move. Movement should not be confused with locomotion.

Locomotion requires a change of position while movement does not necessarily require a change of position. For instance, plants undergo bending movements while remaining on the same point. Animals on the other hand can move from one point to another (locomotion).

When a plant is put in a dark room, it will attempt to move or bend towards light. This is known as positive phototaxis.

You can read on Motion here.


2. Respiration: Majority of organisms require oxygen to stay alive. Respiration is quite different from breathing.

Breathing implies the exchange of gases. For instance, organisms breathe in oxygen (inhalation) and breathe out carbon(IV)oxide (exhalation). Conversely, respiration focuses on the use of the inhaled oxygen.

Inhaled oxygen is used for oxidizing or breaking down digesting food (usually glucose) to produce energy (ATP); and this is what aerobic respiration entails.

Glucose is a simple sugar derived from the breakdown of carbohydrates (complex sugars).

Please read on sugars here.

Carbon(IV)oxide and water are waste products from aerobic respiration, thus organisms breathe them out.

Note: Respiration can also be anaerobic if food is broken down in the absence of oxygen.

Respiration occurs in an organelle of the cell called mitochondria and ATP is generated in the process.

ATP is an acronym for (Adenosine Tri Phosphate).

From the above fact, the mitochondria is often regarded as the power house of the cell.

Please read on global acronyms and their meanings here .


3. Nutrition: All living organisms must feed to stay alive. Without food, organisms will not grow, reproduce and excrete.

Some organism manufacture their own food and are referred to as autotrophs while others depend on ready made food, thus are referred to as heterotrophs.


4. Irritability: All living organisms must be able to respond to stimuli if the are to survive in their environment. A desert plant will have its root penetrating deep within the soil in order to get water.

Based on survival instincts, All animals will attempt to fight or run for survival whenever they sense danger.

Please read on the Uniqueness of Man here.

Note: A stimulus is anything that can elicit a physiological response in an organism. Stimulus can be either external or internal.

The sense organs (eyes, nose, ear, tongue and skin) acts acts as sensory receptors to external stimuli. Examples of stimuli includes touch, pressure, heat, cold, light, pain, water, sound, chemicals and so on.

Please read on Homeostasis here.

Another name for irritability is Sensitivity


5. Growth: All living organisms must grow in size and mass. The food we eat (preferably protein) provides the basis for our growth and the repair of worn out tissues.


6. Excretion: All living organisms must remove metabolic waste product form their body. Metabolic waste products includes water, urea, carbon(IV)oxide and so on.

Feces is NOT a metabolic waste product. This is because it isn't produced from the body cells. Rather, they are undigested materials that didn’t even enter the body cells in the first instance.

In larger animals, The removal of solid undigested materials from the anus is termed as egestion.


7. Reproduction: All living organisms have the ability to reproduce; that is, give birth to their young or offspring. Reproduction ensures the continuity of life for the various species of organism.

Living organisms reproduce in two ways:

Sexually: These require the sex cells of the male and female organisms. The male sex cell is the sperm while that of the female are the eggs or ova.

When both sex cells meet (usually inside the female, but could also take place externally), fertilization occurs and a zygote is formed from the process.

The reproduction involving sperm and egg is termed sexual reproduction.

Please read on the Male Reproductive System here.

Asexually: This form of reproduction requires only one parent organism. No sex cells (sperm and egg) are involved.

The parent organism reproduces by dividing itself (cell division or binary fission), by budding, spore formation or some other means.

Reproduction in this manner is termed asexual reproduction.

Please read on Asexual Reproduction in Plants (Plant Propagation).


8. Death: All living organism must die. After death occurs, an organism will be considered as non-living because it cannot carry out other life characteristics.

Normally, living organisms are expected to grow and mature before they die.

Death is said to occur when a living organism cannot carry out the other basic characteristics of life


9. Adaptation: All living organisms must adapt to their environment if they are to survive. For instance, a fish is able to live in water because it has gills and fins.

Also, a camel is able to survive in the desert because it has large feet to aid walking on sand without sinking. It also has long eyelashes to help protect it from the blowing sand and wind.

The point is:

All organisms have various features on them that enables them adapt within their habitat.

Please read on Immunization here.

Note: Plants are also able to live in different habitats because they have the required adaptive features towards that habitat. For instance:

Plants that live in/on water are termed hydrophytes.

Plants that live on land with moderate amount of water are termed mesophytes.

Plants that live on deserts or arid lands are termed xerophytes.


10. Competition: Due to the limitation of resources, all living organisms must be able to compete for the necessary available resources if they are to stay alive.

The limited resources include food, water, light, mates, space and so on.

You may have observed that male lizards (with red necks) map out their territories in order to enjoy all the resources within it. They will usually undergo fierce competition from their male counterparts before such territories can become theirs.

Please read on the Characteristics of Reptiles here.

This form of behavior in male lizards is termed territorial behavior or territoriality.

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Alfred Ajibola is a Medical Biochemist, a passionate Academician with over 7 years of experience, a Versatile Writer, a Web Developer, a Cisco Certified Network Associate and a Cisco CyberOps Associate.

Amazing facts in Biology

Male Seahorses actually give birth to their young ones, NOT the female

All babies are born with blue eyes

Research made at the University of Vienna suggested that yawning may play an essential role in cooling the brains

All voluntary and concious activity of right handed people are controlled from the left part or hemisphere of the brain

A snail can actually sleep for 3 years 😁

An adult human being is composed of about 60% water. In fact, a newly born baby is composed of about 80% of water. This will drop to 65% after a year and finally to about 60% as the child ages

Without saliva, food can never be enjoyed. Food becomes tasteless since saliva is needed to dissolve the chemicals present in food onto the tongue’s taste buds.

Saliva also contains an enzyme called salivary amylase or "ptyalin" which helps to digest cooked starch to maltose. Maltose is a double sugar or disaccharide. Please read on sugars here


During strenuous exercises like sprinting or 🏃 running, your body may actually work in the shortage of oxygen. During this time, your body owes oxygen (called oxygen debt) and it must be replenished or repayed after the exercise is stopped. This is why you breathe excess of oxygen after you stopped the exercise.

This is the concept of anaerobic respiration

A food Chain is a diagram that shows the relationship between plants and animals within a habitat on the basis of how they rely on each other for food.

Note: Habitat is a place where an organism live. It is of three types:

  • Terrestrial (Land)
  • Aquatic (Water)
  • Arboreal (🌲 Treetops)

You can read on Food Chain here

The term Biology originated from two Greek words. They are:

  • Bios: means life. 
  • Logos: means knowledge or to study.

Biology can therefore be defined is the study of life

Anything that has life is generally considered as a living organism (or organism) 🌱🐐🐓. All living organisms must be able to carry the following activities:

  1. Movement
  2. Respiration
  3. Nutrition
  4. Irritability or Sensitivity
  5. Growth
  6. Excretion
  7. Reproduction
  8. Death
  9. Adaptation
  10. Competition

The above listed points are often regarded as the basic characteristics of life. You can memorize them using the acronym (MR. NIGER DAC).

You can read on the introduction to Biology and the basic characteristics of life here

The gas used in the manufacture of food by plants is Carbon dioxide or Carbon(IV)oxide or CO2. 

Plants manufacture food through a process called photosynthesis. Please read on photosynthesis here

Note: Plants are the only orgnisms that take away CO2 from the atmosphere

In the Biological organization of life, it is said that cells form tissues, tissues form organs and organs form systems. There are 12 systems in the human body; these are:

  1. Cardiovascular System
  2. Digestive System
  3. Endocrine System
  4. Immune System
  5. Integumentary System
  6. Lymphatic System
  7. Muscular System
  8. Nervous System
  9. Reproductive system
  10. Respiratory System
  11. Skeletal System
  12. Urinary or Renal System

Please read on the amazing facts in Biology here