Chapter 1 Characteristics and classification of living organisms | 1.
1 Characteristics of living organisms
What makes something alive? Let's explore!”
a) Movement (b) Respiration
Definition: Movement is an action by an Definition: Respiration involves chemical
organism or part of an organism that reactions in cells that break down nutrient
causes a change of position or place. molecules to release energy for
Examples: metabolism.
• Animals: Walking, swimming, flying (e.g., Types:
humans, fish, birds). • Aerobic respiration: Using oxygen to
• Plants: Slow movement, like sunflower release energy.
heads turning to face the sun. • Anaerobic respiration: Releasing energy
without oxygen (e.g., in yeast).
Why It Matters: Movement helps organisms
find food, escape danger, or get sunlight. Why It Matters: Provides energy for all life
processes like growth, movement, and
repair.
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(c) Sensitivity
(d) Growth
Definition: Sensitivity is the ability to
Definition: Growth is a permanent increase
detect and respond to changes in the
in size and dry mass.
internal or external environment.
Examples:
Examples:
• Animals: Growing from a baby to an
• Animals: Sensing danger and running
adult.
away.
• Plants: Growing roots, stems, and leaves
• Plants: Closing leaves when touched
over time.
(e.g., mimosa plant).
Why It Matters: Growth ensures the
organism can carry out essential functions
Why It Matters: Helps organisms adapt to
like reproduction.
their environment and survive.
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(e) Reproduction (f) Excretion
Definition: Reproduction is the process by Definition: Excretion is the removal of
which organisms produce more of their waste products of metabolism and
own kind. substances in excess of requirements.
Types: Examples:
• Sexual reproduction: Involves two • Humans: Exhaling carbon dioxide,
parents, creates genetic diversity. sweating, and urination.
• Asexual reproduction: Involves one • Plants: Releasing oxygen as a by-product
parent, offspring are identical. of photosynthesis.
Why It Matters: Ensures the survival of a Why It Matters: Prevents the accumulation
species over time. of harmful substances in the body.
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(g) Nutrition
Definition: Nutrition is the taking in of
materials for energy, growth, and
development.
Examples:
• Plants: Photosynthesis to produce
glucose.
• Animals: Eating food for nutrients.
Why It Matters: Without nutrition,
organisms wouldn’t have the energy to
grow, move, or reproduce.
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C. Respiration
Respiration is the process by which cells break down nutrient molecules (e.g., glucose) in
the presence of oxygen to release energy. This energy is used for various cellular activities
necessary for survival.
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Correct answer: C. 2, 3 and 4 only.
Egestion: The removal of undigested food from the body. Not all
living organisms ingest food, so not all carry out egestion.
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The correct answer is B. The microorganisms show:
• Movement: They move towards light.
• Nutrition: They perform photosynthesis using chloroplasts.
• Sensitivity: They respond to the light stimulus.
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Chapter 1 Characteristics and classification of living organisms | 1.2 Concepts and uses of classification systems
Concept and Uses of Classification Systems
Organisms are grouped based on shared Defining a Species
characteristics, which helps scientists study • A species is defined as a group of
and understand the vast diversity of life. organisms that can interbreed and produce
fertile offspring.
• Classification organizes organisms into
hierarchical groups such as Kingdom, • Fertile
offspring are capable of
Phylum, Class, Order, Family, Genus, and reproducing, ensuring the continuation of
Species. the species.
• Uses of classification include: • Example: While a horse and a donkey can
◦Facilitating the identification and produce a mule, the mule is infertile,
naming of organisms. indicating that horses and donkeys are
◦Understanding evolutionary relationships separate species.
between species.
◦Aiding in scientific communication by
providing a universal naming system.
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The Binomial System of Naming Species
• The binomial nomenclature system
provides a unique, universally recognized
scientific name for each species.
• The name consists of two parts:
1.Genus (first part, capitalized)
2.Species (second part, lowercase)
• Example: Homo sapiens is the scientific
name for humans.
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Constructing and Using Dichotomous Keys E.g
Dichotomous keys are tools used to identify
organisms based on their observable
characteristics.
• The keys present a series of paired
statements or questions that describe
characteristics of organisms.
• Each pair offers two choices, leading to a
further division until the organism is
identified.
• Dichotomous keys are constructed using
identifiable features like shape, size, color,
presence or absence of specific traits, etc.
• Example of a dichotomous key question:
"Does the organism have wings? (Yes/No)"
leads to the next set of questions based on
the answer.
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C. A species
A species is defined as a group of individuals that can reproduce to produce fertile
offspring. This is the primary criterion used to determine whether individuals belong to
the same species.
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C. They are the same genus but not the same
species.
Explanation: Modern humans (Homo sapiens)
and their ancestors (Homo heidelbergensis, Homo
erectus, and Homo habilis) all belong to the
same genus (Homo), but they are different
species within that genus.
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A. W and X have the most differences (5 differences)
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Correct answer: D. They share an ancestor.
An identical sequence of amino acids in a protein suggests a high degree of genetic similarity between the animals.
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Chapter 1 Characteristics and classification of living organisms | 1.3 Features of organism
3. Fungus Kingdom
Features of Organisms
• Definition: Organisms are classified based
on shared features.
• Purpose: Classification helps in identifying,
studying, and understanding relationships
between different organisms.
4. Protoctist Kingdom
Main Features for Classifying Organisms into
Kingdoms
• 5 Kingdoms Classification:
1. Animal kingdom
5. Prokaryote Kingdom
2. Plant kingdom
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Classifying Vertebrates
• Main Groups of Vertebrates:
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a) Fish e.g. sharks
b) Amphibians e.g. frog, toad
c) Reptiles e.g crockdiles, lizards, snakes, turtles and tortoises
d) Birds e.g. kingfisher and eagles
e) Mammals e.g. humans, cats and lions
Classifying Arthropods
Arthropods are animals with jointed legs but no backbone.
a) Insects e.g. dragon fly, house fly and grass hoppers
b) Crustaceans e.g. crabs, lobsters and woodlice.
c) Arachnids e.g. spiders, ticks and scorpions.
d) Myriapods e.g. centipedes and millipedes
Classifying Plants
The main groups of plants are:
1. Ferns:
2. Flowering Plants:
Viruses and Their Features
• Definition: Viruses are non-
cellular entities that can only
reproduce inside a host cell.
• Main Features:
1. Protein Coat: Protects the virus
and helps in attaching to host
cells.
2. Genetic Material: Either DNA or
RNA, contains instructions for
making new viruses.
Correct answer: A. Feathers.
Feathers are a unique characteristic found only in birds
and are used for classification purposes.
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