CLASS: SS1

SUBJECT: BIOLOGY                                PERIOD(3)

TOPIC: REPRODUCTION

SUBTOPIC 1: REPRODUCTION IN UNICELLULAR ORGANISMS

SUBTOPIC 2: REPRODUCTION IN INVERTEBRATES

PREVIOUS KNOWLEDGE: Students are familiar with the topic

OBJECTIVES: At the end of the period

The students should be able to Define reproduction State the types of reproduction

iii.      Explain in details the types of asexual and sexual reproduction

Period 2:

Describe reproduction in Amoeba Describe reproduction in Paramecium

iii.      Describe reproduction in spirogyra

 

Period 3:

Describe reproduction in earthworm Describe reproduction in cockroach

iii.      Describe reproduction in Housefly

Describe Reproduction in snail. Describe reproduction in toad Differentiate between complete and incomplete metamorphosis

References

Essential Biology for Senior Secondary Schools 1-3, by M.C Michaels pg 244 – 251.

 

Content

Reproduction is the process by which living organisms produce offspring (new individuals) of their type. Reproduction is of 2 types namely.

Asexual reproduction – an individual produces an offspring by itself, that is, a single parent without production of gamates or fusion of nuclei. Closes (offspring which are identical to the parent) are produced. Asexual reproduction is common among single organisms, flowering plants and in organisms which can produce both sexually and asexually depending on certain conditions (food availability, favorable environmental conditions for growth) the types of asexual reproduction include: Binary fission: The parents organisms simply divides into 2 or more parts by mitosis, each of which can exist by itself. If the cells divides into more than 2 cells, it is referred to as fission e.g. in bacteria and  protists e.g. of Binary fission Amoeba, Paramecium. Budding: In this types, the offsprings develops as an outgrowth of the parent. The bud may form an external or internal surface of the parents. Internal buds are formed in some sponges and are released when the parents dies. External buds occur in Hydra, coral polyps and yeast. These buds break off from the parent without causing any injury and lead an independent life.

iii.      Spore formation: Spores are small unicellular bodies which are produced in large numbers. They are small light and dispersed by the wind. Spores are usually produced by fungi, mosses, ferns, algae, protists and bacteria.

Fragmentation – a part of an organisms breaks up or fragments and give rise to a new organism. It occurs in algae, coelenterates and sponges e.g. planaria, spirogyra Vegetative propagation – occurs mainly in higher plants. A new plant grows from any portion of an old one other than the seeds e.g. stems and roots. Patogenesis – is a natural form of asexual reproduction in which growth and development trof embryos occur without fertilization, that is developed from an unfertilized egg cell e.g. aphids, honey bee, ants, wasps. Some scorpions, some plants, nematodes, water flies, some mites, some fish, amphibians and reptiles.

vii.     Schizogony – this is the asexual reproduction of a sporozoite by multiple fission within the body of the host giving rise to merozoites. This type is found in some protozoa especially parasitic sporozoans e.g. malaria parasite  plasmodium

Sexual reproduction: Offsprings are produced by the fusion of 2 different sex cells which usually come from 2 different parents.

 

Reproduction in Amoeba

Amoeba reproduces asexually by splitting or dividing into two equal parts by mitosis to produce 2 new daughter cells (binary fission)

 

REPRODUCTION IN PARAMECIUM

Paramecium reproduces asexually (binary fission) and sexually (conjugation). Conjugation in Paramecium involves the pairing of a whole cell with another whole cell both of which as a gamete and exchange nuclei.

 

REPRODUCTION IN SPIROGYRA

Spirogyra reproduce sexually (conjugation) and asexually fragmentation) in conjugation, 2 filaments (conjugants) lie side by side and produce outgrowths which meet and form the conjugation tube. The cell cytoplasm shrinks away from the cell walls and round up to form a gamete. One acts as the male and migrates through the conjugation tube into the other cell and fuse forming a zygote or zygosphere which germinates and forms a new filament. It also occurs  in mucor rhizopus and paramecium.

 

Fragmentation in spirogyra occurs when a filament reaches a certain length, parts of its break away and grow into new filaments.

 

REPRODUCTION IN EARTHWORM

Earthworm reproduces sexually and the fertilization is internal. Matured male and female earthworms came together and mate. The male injects sperm into the female reproductive organs. After fertilization, the female lays numerous eggs which hatch into small and tiny baby earthworms which develop into adulthood.

 

REPRODUCTION IN COCKROACH

Metamorphosis is the series of gradual changes of form and shape of certain organisms from the fertilized egg (immature stage) to adult (mature stage) and there are 2 types Complete (Egg – larva-pupa – adult) e.g. mosquito, housefly, wasp, beetles, bees, butterfly and incomplete (egg – nymph – adult) e.g. grasshopper, termites, dragonfly, aphis, cockroach, prayingmatis, locust etc.

 

Reproduction in cockroach, is sexual and internal fertilization occurs. The male introduce sperms into the female where it is stored in sperm pouch from which the sperm fertilizes the eggs. The eggs of cockroach are laid in a horny egg case called ootheca which is chitinous in nature. The case contains 10-15 egg and are arranged in 2 rows of 5-8 eggs per row. These egg cases are deposited in a dark, warm and humid place where they hatch after about 30 – 100days into nymphs (very small, wingless and colourless organisms) Nymptial  life lasts for 10 – 16 days during which series of moulting occur to develop wings and grow bigger.

 

The appearance of wings shows adulthood. An adult cockroach has well developed parts. The lifecycle is about 11 – 20 months.

 

 

REPRODUCTION IN HOUSEFLY

Housefly breeds on any decomposing organic material and it exhibits complete metamorphosis. The life cycle is short about 3-4weeks. After fertilization, the female lays 2-7 batches of eggs (100 – 150 eggs per batch) in moist decomposing matter and these hath out in 8 hours to 3 days into which larvae maggot). The Larval body is made up of 12 segments and it possess the head which has a pair of hooks for tearing food dn to draw it along and 2 pairs of spiracles (on the 2nd and 12th segments. It moults, shedstis skin) several times and last for about 5 -14 days to begin pupal stage. The maggot shortes and theskin forms the puparium (pupal case). It doesn’t feed or move at this stage because internal reorganization of the body is taking place. The pupal stage takes 3-10 days after which the adult emerges from the puparium using a sac-like organ (ptilinum) on its head.

 

 

REPRODUCTION IN SNAIL

Snail reproduces sexually and its fertilization  is internal. The female lays the eggs in a cool dry place. Baby snails hatch and emerge from the eggs after some days.

 

Reproduction in toad

Snail reproduces sexually and the fertilization is internal. The female lays the eggs in a cool dry place. Baby snail hatch and emerge from the eggs after some days.

 

RERPODUCTION IN TOAD

Toad reproduces sexually and fertilization is external. As the female lays her eggs, the male releases its sperms on them. The eggs are surrounded in strings of jelly (the jelly separates the eggs to receive enough oxygen, protect mechanical injury, prevent bacterial  and fungal attack and from drying-up. Toad undergo metamorphosis from egg to adult stage the tadpole emerge from the egg after 1-2 days and grow. It feeds on the egg yolk at first due to the absence of  mouth and breathes through the skin. It attaches itself to a water weed using a sticky substance secreted by a V-shaped cement gland.

 

The tadpole develops 3 external gills on either side of the head and horny jaws for feeding on water weeds(herbivore) After 6-10 days after hatching, the external gills disintegrate and the internal gills develop. A gill cover (operculumO avers the gills leaving an opening called spout on the left side through which water flows out. The limbs develop, mouth replaces horny jaws and the tadpole starts eating small animals. A young toad develops after reabsorption of the tail. The process takes a total of about 40-45days. Thyroid gland at the region of the head and turn a hormone called thyroxine which controls metamorphosis in amphibians. Absence of this hormone / iodine deficiency prevents or inhibits metamorphosis.

 

INSTRUCTIONAL MATERIALS: Textbooks, pictures; videos showing reproduction.

Teaching methods procedures

Step I: teacher revises the topic and introduce the new logic

Step II: Teacher explains metamorphosis in insects and toad

Step III: Teacher explains reproduction in unicellular organisms and invertebrates

Step IV: Teacher allows students to ask questions and writes notes under content on the board.

CLASSROOM (ACTIVITIES)

PERIOD 1: Students discuss reproduction types

PERIOD 2: Students discuss reproduction in unicellular animals.

PERIOD 3: Students discuss reproduction and metamorphosis in invertebrates

EVALUATION:

PERIOD 1: What is reproduction?

PERIOD 2: Explain conjugation in paramecium

PERIOD 3: Explain courtship in toad

 

SUMMARY/CONCLUSION: Teacher summarizes the topic, makes the students notes and makes corrections where necessary.

 

ASSIGNMENT(S)   

PERIOD 1: In a tabular form, differentiate between sexual and asexual reproduction

PERIOD 2: Differentiate between complete and incomplete metamorphosis.

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CLASS: SS3

SUBJECT: BIOLOGY                                                    PERIOD(S) 3

TOPIC: MECHANISM OF TRANSPORT IN HIGHER PLANTS

SUBTOPIC 1: TRANSLOCATION AND TRANSPIRATION

SUBTOPIC 2: WATER ABSORPTION AND TRANSPORT

SUBTOPIC 3: DIFFERENCES IN PLANT AND ANIMAL TRANSPORT

PREVIOUS KNOWLEDGE: Students are familiar with the topic

 

OBJECTIVES: At the end of the period

Students should be able to:

PERIOD 1:

Discuss the mechanism of transportation in plants Describe the tissues involved in the transportation of material

PERIOD 2:

Explain how manufactured food, water, mineral salts, and other materials are transported in plants.

PERIOD 3:

List the differences between transport in plants and animals. Demonstrate experimentally the flow of materials in plants

REFERENCES:

Essential Biology for Senior Secondary Schools by M.C Micheals pg 292 – 300

Modern Biology for senior secondary schools pg 312 – 317

 

CONTENT

In a simple plant (algae), materials enter or leave the body cells by diffusion (gases) manufactured food and waste products) and water enters by osmosis. In higher land plants, vascular tissues (special conducting tissues) carry out transport with latex tubes to assist. The major materials transported in plants are gases (CO2 and O2), water, mineral salts, manufactured food, nitrogenous waste products, hormones and pigments. Plant saps, cell sap and cytoplasm are the main transport media. Gases are mainly absorbed through the stomata (in the leaves) and lenticels (in the stem).

         

Water and mineral salts are absorbed through the root system, water, mineral salts and soluble food are transported in the vascular tissues of the plant. The vascular tissue are made up of a network of long tubes called vascular bundles. A vascular bundle consists of the xylem and phloem tissues. The cambium exists between the xylem and phloem tissues in the roots and stems of dicotyledonous plants.

Cambium – are made up of narrow living cells with thin walls and dense cytoplasm. Cambium produce secondary xylem and phloem by dividing and multiplying. This growth in width (girth) of the stem is called secondary thickening. Xylem tissues – consists of dead cells with lignified cell walls. Xylem transport water and dissolved mineral salts from the roots to other plant parts. It also give support and rigidity to plants.

iii.      Phloem: Consists of thin walled living cells with dense cytoplasm which have perforated cross walls. Phloem transports a manufactured food from the leaves to other plant parts.

 

TRANSLOCATION

This is the process by which manufactured food is transported from green leaves of a plant to all the living plant cells especially those in the actively growing regions (root tips, stem tips and buds) and excess food is also stored. Phloem is responsible for this. Glucose, oil, resin, protein, alkaloids and hormones are among the translocated materials.

 

TRANSPIRATION

Transpiration is the loss of water from the leaf surface of plants by evaporation. The continuous flow of water from the roots to the leaves is called the transpiration stream. Plants loose excess water through the stomata (stomata transpiration), lenticels (lenticular transpiration) and the leaf cuticle (cuticular transpiration). Transpiration is affected by the following factors:

Temperature – increase in temperature causes increase in transpiration rate Wind – increase in wind causes increase in transpiration

iii.      Soil water-high level of soil water results in higher absorption and transpiration rate.

Light – High light intensity results in high photosynthetic rate leads to increase in temperature and therefore, increase in transpiration. Humidity: Higher humidity leads to reduce rate of transpiration and vice versa. size of stomata pores – when the guard cells become turgid and the stomata open leading to transpiration however when the guard cells are flaccid, the stomata close and transpiration stops.

 

WATER ABSORPTION BY PLANT ROOTS

The cell sap in the root hairs is more concentrated than the soil water. The cell membrane of the root hairs is selectively permeable therefore, soil water enters the vacuole of the root hairs via osmosis. The extra water causes increase in tugor pressure of the vacuole (reduce osmotic pressure) and forces water out into the cell walls towards the cortex. The cell next to the root hair on the inside has a lower turgor (higher osmotic pressure) hence water will pass into it by osmosis. This process enables water absorbed to get to the xylem vessels.

 

TRANSPORT OF WATER IN THE XYLEM TISSUE

Water transport by the xylem is due to the following process

Capillary action: This allows the upward movement of water through the xylem from the roots to the leaves. The xylem vessels form very fine capillary tubes. Root pressure and suction pressure – Osmotic pressure difference between the cell sap and soil nutrients concentration create root pressure. The cell sap becomes more concentrated and it tends to draw up the nutrients. Suction pressure occurs during stomata transpiration. This pressure facilitates the movement of water from the soil to the xylem tissues.

 

iii.      Transpiration stream or pull

 

SIMILARITIES IN TRANSPORT IN ANIMALS AND PLANTS

A liquid medium is required Materials are transported in dissolved form. Tabular or cylindrical vessels are necessary Diffusion and Osmosis play key roles in transportation

 

 

 

DIFFERENCES BETWEEN PLANTS AND ANIMALS

 

PLANTS

ANIMALS

1

Media from transportation is cell sap

Blood is the medium of transportation `

2

Root pressure or transpiration generates forces for pull

Heart generates forces for transport of nutrients.

3.

The transport medium is not tissue

Transport medium is made up of cells of different types of tissues.

4.

Materials are transported through different vessels (xylem and phloem)

Materials are transported in the same vessels(blood vessels)

 

INSTRUCTIONAL MATERIALS – PICTURES AND VIDEOS ON TRANSPORTATION INPLANTS

TEACHING METHODS PROCEDURES

Step 1: Teacher revises the previous topic and introduce the new topic

Step II: Teacher explains how materials get transported in plants.

Step III: Teacher explains absorption of water and mineral salts by the root hairs.

Step IV: Teacher lists the differences between transportation in plants and animals.

Step V: Teacher allows students to ask questions and writes notes under content on the board.

 

CLASSWORK (ACTIVITIES)

PERIOD 1: Students discuss transportation of materials in higher plants

Period 2: Students discuss the vessels of transportation and how they carry out their functions

Period 3: Students list the differences in plants and animal transport.

 

EVALUATION

PERIOD I: Explain transport in higher plants

PERIOD 2: State the function of

Xylem Phloem

PERIOD 3: List 3 factors affecting transpiration

 

SUMMARY/CONCLUSION: Teacher summarizes the topic, marks the notes of the students and make corrections where necessary.

 

ASSIGNMENT(S)

Describe an experiment to show the translocation occurs through the phloem tissue. Describe an experiment to demonstrate transpiration in plants. Describe an experiment to show that water is conducted in the xylem tissue of flowering plants. Describe an experiment to demonstrate root pressure and transpiration pull.

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