Living things and non living things – Characteristics and Classification, Plants and animals

CONTENT

• Characteristics of Living Things
• Differences between Plants and Animals
• Classification of Living Things

CHARACTERISTICS OF LIVING THINGS

Everything in nature can be classified into two groups: living and non -living things.

The living things can be distinguished from their nonliving counterparts through the following characteristics observable in all living things:

1. MOVEMENT: Animals can move from place to place on their own in search of food. Higher plants move certain parts of their body in response to growth or external stimuli
2. RESPIRATION: In order to perform the numerous life processes, living things need much energy. The energy can only be obtained when the organism respires. Therefore, respiration is the oxidation of food substances in the presence of oxygen to produce energy with carbon (iv) oxide and water released as by products.
3. NUTRITION: The act of feeding is called nutrition. All organisms need food to carry out their biological activities. Green plants can manufacture their food. Hence, they are autotrophs  while animals are dependent on plants for their food, so they are heterotrophs.
4. IRRITABILITY: Is the ability of living things to respond to external and internal stimuli in order to survive. External stimuli may be light, heat, water, sound or chemical substances.
5. GROWTH: this is the tendency of organisms to increase irreversibly and rapidly in length and size and in mass. The essence of growth is to enable organisms to repair or replace damaged or old tissues in their bodies. The food eaten by an organism provides the basis of growth.
6. EXCRETION: Toxic waste products of metabolism & other unwanted materials have to be eliminated to ensure proper functioning of the bodies of organisms. Such wastes include water, carbon (iv) oxide etc.
7. REPRODUCTION: Is the ability of a living organism to give birth to young ones (off springs). The essence is to ensure life continuity. Reproduction can be sexual  (involving two organisms) or  asexual (involving one organism)
8. LIFE SPAN / DEATH: Every organism has a definite and limited period of existence. Life , for all organism has five main stages , namely : origin ( birth ) , growth, maturity,  decline and death.
9. COMPETITION: Living things tend to struggle for the basic things of life in order to survive. Hence, they compete for food, water, light, mates and space.
10. ADAPTATION: To survive, every organism possesses ability to get used to change in its environment.

EVALUATION

1. State the characteristics that must be possessed by an organism to be referred to as living things.
   1. Which of these characteristics does a virus possess.

DIFFERENCES BETWEEN PLANTS AND ANIMALS

All living organisms can be generally classified as plants or animals. However, plants can be distinguished from animals in the following ways:

	PLANTS	ANIMALS
1.	Undergo passive movement.	Undergo free or active movement with well developed organs of locomotion.
2.	Gaseous exchange takes place through the entire body.	Gaseous exchange is through special organs.
3.	Green plants photosynthesize i. e. they are autotrophs.	Animals do not photosynthesize i. e. they are heterotrophs.
4.	They exhibit slow response to stimuli.	They exhibit fast response to stimuli.
5.	Growth is apical and indefinite (continuous).	Growth is uniform and definite (limited).
6.	No specialized sense organs.	Possess specialized sense organs.
7.	No specialized excretory systems.	They have special and well developed excretory systems.
8.	Cell has rigid non living cellulose cell wall which provides mechanical support.	Have thin, flexible cell membrane. Mechanical support is provided by external exoskeleton or internal endoskeleton.
9.	They store food (carbohydrates) as starch except fungi which store food as glycogen.	They store carbohydrates as glycogen

EVALUATION

1. Differentiate between autotrophs and heterotrophs
2. State four differences between plants and animals

CLASSIFICATION OF LIVING ORGANISIMS

Nature comprises millions of organisms, hence the need for identification, naming and classifying them in a meaningful manner. The present and widely accepted method of classification of organism was introduced by Carolus Linnaeus. The study of the general principles of classification is called taxonomy or systematic.  Classification is an arrangement of organisms into groups, each group is then split into smaller groups and the members of each group have certain features in common which distinguish them from other groups. The largest group of organisms is the kingdom.  The arrangement of living organisms from the highest to the lowest (with decreasing variety of organisms) is as follows: KINGDOM       >   PHYLUM OR DIVISION   >     CLASS   >       ORDER     >   FAMILY   >    GENUS  > SPECIES    

BINOMIAL NOMENCLATURE

This is the standard system of naming living organisms. Each type of organism is given two names:

(i)         The name of the genus (generic name) to which the organism belongs.

(ii)        The name of the species (specific name) to which it belongs.

The generic name is always written first using initial capital letter (underlined or italicized) e.g. Homosapiens   is man’s scientific name.

EVALUATION

1. Define taxonomy.
   1. What is binomial nomenclature.

GENERAL EVALUATION

1. Explain the differences between growth in plants and animals
2. Define the following characteristics of living things  (a) respiration   (b) irritability                          (c) excretion
3. What are the similarities between living and non-living things
4. What are the similarities between plants and animals
5. Define (a) species (b) genus (c) phylum in classification of organisms

READING ASSIGNMENT

College Biology, chapter 1, page 1 – 6.

WEEKEND ASSIGNMENT

1. The ability of living things to get used to their environment is ____    (a) survival                            (b) adaptation    (c) adjustment   (d) photosynthesis 
2. Response to stimuli in animals can be said to be _______   (a) very slow  (b) very flow  (c) fast (d) steady.
3. Fungi store their food (carbohydrate) as _____   (a) starch   (b) glycogen  (c) hormone   (d) antibody
4. Sensitivity of a living organism to external factor around it is technically known as ________     (a) alertness    (b) irritability    (c) sense organ    (d) knowledge
5. Which of the following is the lowest in the category of classification?   (a) Class           (b) Species      (c) Family     (d) Genus

THEORY

1. With five of the characteristics above, distinguish between plants and animals.
2. Classify human being fully.