Development in Plants and Animals

Development in Plants and Animals

Introduction
In senior one, you learnt about specialised cells and how cells combine to form tissues and then organs. In chapter 8, you also learnt that organisms are made up of cells which divide continuously during the process of mitosis. As cells divide and grow, they change in shape and form and start to perform
different functions and this brings about development. In this chapter you will understand that as organisms grow, they develop specialised cells, tissues and organs which lead to change in structure
and function.
9.1: Differentiation of Cells
A mature multicellular organism usually has millions of cells in its body which begun from a single cell. These cells change in structure and form specialised organs to perform different functions a process known as differentiation of cells. This results into formation of different types of cells depending on their
position in the organism. In Activity 9.1, you will find out why differentiation of cells is important.

Activity 9.1: Analysing the need for differentiation of cells as multicellular plants and animals row
Do this activity in a group.
Key question: What is the importance of differentiation of cells?
What you need: Reference materials about cell differentiation in plants and animals, the Internet, a notebook, a pen
What to do:

1. Research about specialised cells in plants and animals and; List the examples of such cells.
   ii) State the functions of each of the cells identified.
2. Explain the importance of cell differentiation in multicellular plants and animals.
   Present your finding to the class for a discussion.

9.2: Secondary Growth in Dicotyledonous Plant Stems

In plants, the process of cell differentiation occurs in the meristems (the tips of shoot and root). Above the region of cell differentiation, the tissues formed do not undergo any further cell division but form a permanent tissue which then undergoes a process of secondary growth. This usually results into increase in thickness of the trunk. What is secondary growth?

Activity 9.2, you will explore the process of secondary growth of stems in dicotyledonous plants.
Activity 9.2: Exploring the process of secondary growth of stems in dicotyledonous plants
DO this activity in a pair.
Key question: How does secondary growth occurin stems of dicotyledonous plants?
what you need: A chart with the transverse sections of a dicot stem before and after secondary growth, reference materials about growth of stems in dicotyledonous plants, a notebook, a
pen

1. Study the pictures provided below or on the chart.

i) Which differences do you note?
ii)How do you think the differences noted came about?
iii)Using conclusions from your responses above and research,describe the process of secondary growth in dicotyledonous stems.
iv)Why do you think secondary growth is important to the plants?
Share your responses with the rest of the class
9.3: Metamorphosis
Development in insects is seen in a process called metamorphosis. In primary science, you learnt about insect metamorphosis as a series of changes that result into emergence of adult insects from eggs.
The changes that happen du ring metamorphosis assist developing organisms in meeting their lives’ needs. What are the two types of metamorphosis?

In Activity 9.3, you will explore the two types of metamorphosis.

Do this activity in a group.
Key question: What are the differences in the life cycles of different insects?
What you need: Reference materials about the insect life cycles, a pen, a pencil, a note book

What to do:

1. Discuss the different stages of development of a mosquito, a butterfly, a bee and cockroach
2. Using reference materials and/ or Internet, research about the life cycles of the insects in 1) above.
3. Using a pencil, make well labeled drawings of the life cycle of each of the insects above.
4. Which differences do you note in the above life cycles?
5. Classify each life cycle as eithercomplete or incomplete metamorphosis
   Present your findings to the whole class for a discussion.

9.5: Stages of Human Development
You should have noticed that when babies are born, they tend to appear different from the grown up individuals and as they grow they undergo changes in form. This is referred to as development. This development may involve physical, behavioral or cognitive changes. These changes occur as
humans go through the different stages from child hood, puberty stage, adolescence stage to adult hood.

In Activity 9.5, you will recognize and compare the main characteristics of stages of human development.

Activity 9.5: Comparing the main stages of human development from birth to adulthood
Do this activity in a group.
Keyquestion. What are the differences in the stages of development in hUmans?
What you need: Reference materials about stages of human development, a pen, a pencil
Study Figure 9.1

1. Which ofthe pictures represent early childhood, late childhood, infancy, puberty, adolescence, adulthood and old age stages?
2. Using the pictures, the people around you and your personal experiences, identify the characteristics of each stage of development
3. Which differences do you note in the physical, behavioral and cognitive characteristics of the different stages?
4. Describe the developmental stages of a child from birth to late childhood.
   Share your findings with. the rest of the class.

9.6: A o escencean Puberty
Normal development in humans involves the onset of puberty at about 10- 15 years in girls and 13-15 years in boys. This brings about development of secondary sexual characteristics. The period between puberty and adulthood is known as adolescence. This stage involves different physical, physiological, psychological and behavioral changes. In Activity 9.9, you will explore these changes.

Activity 9.6: Understanding the changes associated with puberty and adolescence and the associated myths
Do this activity in a group.
Key question: What are changes associated with puberty and adolescence?
What you need: A video clip showing changes at puberty, reference materials about puberty and adolescence, a notebook, pen. Note: Learners with hearing impairments are
encouraged to use the reference materials provided.
What to do:

1. Watch the video clip provided and study the characteristics being shown in the video. Which changes are you able to note as humans go through puberty and adolescence?

2.Apart from the changes identified in 1), which other changes do you think occur in humans during puberty and adolescence?
3.Of the changes identified, which ones have you identified before in the people around you?
4.Have you experienced any of the changes identified? If yes, which ones?
5.How did you feel when you noticed such a change(s) in your body?
6.How were you able to cope up with or handle such a change(s)?
7.What would you advise someone to do in order to cope up with the changes above?
8.What does the community say about these changes which from your discovery is not true?
Share your responses in an open class discussion and harmonise your views.

9.7: The Process of Aging
One of the stages of development in humans is old age which comes along with various changes in one’s physical, physiological, emotional and mental characteristics. See Figure 9.2. If you have ever lived or interacted with an elderly person, which differences did you notice between that person and
yourself?

In Activity 9.7, you will discover the various features related to the process of aging.

Activity 9.7: Discussing the features related to the process of aging.
Do this activity in a pair.
Key question: What are the features related to the process of aging?
What you need: The Internet or reference materials about aging in hu mans, a pencil, a pen and a notebook
What to do:
Study Figure 9.2 carefully
1.
i) What observable differences do you note between the humans in the pictures?
ii) What other differences do you think exist between the two humans shown in the pictures?
iii) From (ii) and from your personal experiences, write down the features associated with the process of aging?
iv) What do you think brings about aging?
Share your responses with other pairs, discuss and agree on the features related to the process of aging.

In this chapter, you have learnt that:
1.Cell differentiation involves cell changes to form specialized organs to perform different functions.
2.In plants, the process of cell differentiation occurs in the meristems.
3.Metamorphosis is a series of changes that result into emergence of adults insects from eggs.
4.Some insects go through four stages of development while others go through three stages.
5.The human development involves physical, behavioral cognitive changes.
6.Aging in humans comes with various physical, physiological motional and mental changes.

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