LOWER V LIFE SCIENCES
MODULE BOOKLET:
How do organisms reproduce?
By the end of this module of work, you will be able to:
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Identify and describe different types of cells.
Determine the different levels of organisation.
Describe the advantages of being multicellular vs. unicellular.
Identify the different types of asexual reproduction in organisms.
Describe how asexual reproduction can occur in plants.
Describe the process of sexual reproduction in plants from
pollination to seed germination.
Identify reproductive organs in plants.
Describe adaptations for pollination.
Identify differences between cross / transversal sections to a
longitudinal section.
Describe the structure and function of the male reproductive system
in humans.
Describe the structure and functions of the parts of the female
reproductive system in humans.
Describe the menstrual cycle in humans.
Describe the process of fertilisation, implantation, and pregnancy in
humans.
Name: _____________________________________
CLASS: _____________________________________
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MULTICELLULAR ORGANISMS AND CELL SPECIALISATION
You have been introduced to cells as basic unit of life. This means that all living organisms
consist of one or more cells. Most of the organisms that we are familiar with i.e., plants and
animals, are multicellular which means made up of many cells.
Can you think of some advantages to being multicellular?
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You have studied two categories of cell, plant cells and animal cells and have noted some of the
differences between them. We need to consider some of the consequences of these differences.
What are the advantages of having a cell wall?
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What advantage might there be to not having a cell wall?
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Watch this Amoeba Sisters video:
https://www.youtube.com/watch?time_continue=4&v=wNe6RuK0FfA
Different cells for different functions
When studying plant cells, you looked at a picture of onion cells and examined moss leaf cells
under the microscope. The most striking difference between them was that the leaf cells
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contained many oval green structures called chloroplasts. Onion cells do not contain
chloroplasts because they are part of an underground part of the plant used for storage. Since
chloroplasts absorb light for the process of photosynthesis, there is not much point in cells of
underground structures, like roots, having chloroplasts. In primary school you would have
learned that plants have different parts (biologists call them organs) with different functions:
roots, stems, leaves and flowers. In Biology we find that there is a strong relationship between
structure and function. Cells will be specialised i.e., have certain features / structures to help
them perform a particular function better.
In multicellular organisms, cells can work together to keep the organism alive.
Animal cells are also specialised. The cheek cell which you looked at are just one kind of cell
found in the human body. Their job is to form the lining inside the mouth. Cells that cover or line
structures tend to be arranged in sheets. There are about 200 different kinds of cells in the
human body.
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Below are pictures and a table of some of these cell types.
Match each of the pictures to the cell types listed in the table. Certain parts of the table have
been left blank – fill in the missing information.
Cell Type
Structure
– special characteristics
Disc–shaped, flattened. No nucleus
Skin cells
Function
Protection
Waterproof
To swim to meet an egg cell
Nerve cells
Long and narrow
Store fat where there is an excess
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Levels of Organisation
The living world can study at different levels, starting from what can only be viewed with a
microscopic up to whole ecosystems. Examples of how we organise these different levels in Life
Sciences:
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Cell level: Basic unit of structure and function of all living things.
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Tissue level: Group of cells of the same kind.
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Organ: Structure composed of one or more types of tissues. The tissues of an organ
work together to perfume a specific function. Human organs include the brain, stomach,
kidney, and liver. Plant organs include roots, stems, and leaves.
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Organ system: Group of organs that work together to perform a certain function.
Examples of organ systems in a human include the skeletal, nervous, reproductive, and
digestive systems. The digestive system consists of different organs for example the
mouth, stomach, and the intestines but they all work together to digest your food.
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Organism: Individual living organisms are made up of many organ systems all working
together to carry out the necessary processes of life that we looked at last lesson.
https://study.com/academy/lesson/living-organisms-organization-functions-structure.html
Organisation of digestive organ system in a mouse
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TYPES OF ASEXUAL REPRODUCTION
Characteristics of life:
https://www.youtube.com/watch?v=cQPVXrV0GNA&list=PL8qBZkA9Wl9sYnGCZIP1daV50wcY
yghqOne of the defining characteristics of cells and living organisms is the ability to reproduce. Cells
make more cells. How do they do this?
The simplest way is for a single cell to make a copy of its DNA (the material that contains the
instructions for what the cell should look like (structure) and what it does (functions). A new cell
will need this information. The cell then elongates and splits in two, each half getting one copy of
the DNA. This is called binary fission (binary = two; fission = splitting). Because the DNA
is copied the two new cells will have the exact same set of instructions and so will look identical
and function identically. We call cells like this, clones. A variation of this is budding, where the
new organisms start out smaller than the parent instead of splitting into two equal parts.
Of course, this is easy if the whole organism consists of only one cell. It becomes more
challenging if the organism is multicellular and has lots of different specialised cells. That is why
complex organisms, like most animals (including ourselves) can only reproduce sexually.
We will be focusing on asexual reproduction starting with single celled organisms and a couple
of unusual animals. Then we will be looking at plants who have many ways of reproducing
asexually.
Watch the videos below:
Asexual reproduction:
https://www.youtube.com/watch?v=i9zj9V8OWRk
Types of asexual reproduction:
Watch just the first 3min 30s – you will view the rest in your next lesson.
https://www.youtube.com/watch?v=6Ew6mqwgGR0
Hopefully in watching these videos you came to realise that there are many advantages to
asexual reproduction but also some disadvantages. Try to list some of these.
Advantages and Disadvantages of Asexual Reproduction
Advantages
Disadvantages
Refer to Asexual methods (page 322 and continuing to the top of page 323) in your
Biology For Life textbook
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So, what are some of the differences between sexual and asexual reproduction?
Watch the video link below:
Amoeba sisters: sexual and asexual reproduction:
https://www.youtube.com/watch?v=fcGDUcGjcyk
Activity:
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ASEXUAL AND SEXUAL REPRODUCTION recap
Reproduction is the process whereby an organism produces new individuals (offspring). In
humans and many other organisms, reproduction involves two individuals, the male and female.
We call this sexual reproduction. However, some organisms can reproduce on their own without
another individual. We call this asexual reproduction. Some organisms only reproduce
asexually, some only reproduce sexually, and some can reproduce asexually or sexually.
What is asexual reproduction?
Asexual reproduction involves only one parent. It occurs when an individual produces offspring
that are genetically identical to themselves (i.e., they are clones of their parent). No gametes
(sex cells) are produced, and no mating occurs. Fertilisation does not occur. It occurs mainly on
organisms whose bodies have a simple structure.
What is sexual reproduction?
This type of reproduction involves two parents. Sexual reproduction occurs when individuals
produce offspring that are not genetically identical to the parent. This is because the offspring
contains only half the genes from each parent. To produce offspring sexually, sex cells or
gametes are produced in sex organs. The male gamete must join with a female gamete. The
fusing of a male gamete with a female gamete is called fertilisation and results in a single cell
called a zygote. The zygote develops into an embryo which will grow into a new organism.
WAYS IN WHICH ASEXUAL REPRODUCTION CAN OCCUR:
BINARY FISSION:
This is the division of a cell into two daughter cells that are genetically identical to the parent.
One parent cell will produce two daughter cells. Single celled organisms such as bacteria and
amoebas reproduce in this way.
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BUDDING:
Yeast cells and Hydra reproduce by budding when conditions are favourable. This occurs when
a small outgrowth develops on the parent. Meanwhile, the nucleus is copied. One of the two
resulting nuclei stays in the parent cell and the other one moves into the bud. The outgrowth
becomes larger until it breaks off from the parent. The parent supplies nutrients to the bud while
they are attached. Sometimes the new cell starts budding before it has separated from the
parent cell.
SPORE FORMATION:
Moss, ferns, and fungi produce spores. Spores can survive for long periods in harsh conditions
and can give rise to new individuals that are genetically identical to the parent.
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VEGETATIVE REPRODUCTION:
Many plants can grow new individuals without having to make seeds. For example, if a piece of
a stem from a begonia plant were cut off and one end placed in water, after two weeks, the stem
would have grown its own roots and leaves.
Layering
Grafting
Cutting
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ADVANTAGES OF ASEXUAL REPRODUCTION:
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No need for a partner.
Many offspring are produced quickly.
Can occur when conditions are favourable.
DISADVANTAGES OF ASEXUAL REPRODUCTION:
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Offspring are genetically identical to parent (no new variety is produced). This means that
if the parent has harmful genes, then the offspring would also have them.
ADVANTAGES OF SEXUAL REPRODUCTION:
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Gives rise to variety because offspring are different to parent. Variety is important for
successful continuation of species and adaptation.
There is only a 50 percent chance of passing harmful genes onto offspring. This means
that offspring have a greater chance of being healthy.
DISADVANTAGES OF SEXUAL REPRODUCTION:
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Only 50 percent of an organism’s genes will be passed on to their offspring.
Sexual reproduction does not produce lots of new individuals quickly.
Sexually mature individuals must first find one another (or be near one another) before
offspring can be produced.
Watch this video from 3min 30s onwards:
https://www.youtube.com/watch?v=6Ew6mqwgGR0
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SEXUAL REPRODUCTION IN PLANTS
INRODUCTION TO SEXUAL REPRODUCTION
Introduction to sexual reproduction: https://www.youtube.com/watch?v=LgLkt02Hl9s
Why sex: https://ed.ted.com/on/WI1RRgWY#review
Watch the video, then scroll down and answer the 7 multiple choice questions.
Now go to the link below:
Follow the instructions in which you click on each organism’s picture to read about how it
reproduces and then vote on whether it reproduces asexually sexually or both. If you are right
the answer will turn green, if you are wrong, it will be in red and crossed out. Try again.
https://learn.genetics.utah.edu/content/basics/reproduction/
You are now ready to watch an overview of reproduction in flowering plants.
https://www.youtube.com/watch?v=R8_ScKzLAfE
To consolidate what you have learned, read through the first page of the Flower notes and page
368 in your Biology for Life textbook.
Flowers have the following parts:
Carpels: These are the female reproductive organs and are found at the centre of a flower.
Each has a hollow base, the ovary, which contains a single ovule. An ovule contains the female
sex cell. The ovary eventually becomes a fruit, protecting the ovule which becomes a seed.
Above the ovary there is a narrow style which ends in a stigma. Pollen grains stick to the stigma
during pollination.
Stamens: These are the male reproductive organs. They are arranged in a ring around the
carpels. A stamen consists of a stalk or filament bearing an anther in which pollen grains grow.
Pollen grains contain the male sex cells.
Petals: In most flowers the carpels and stamens are surrounded by a ring of petals. Some
flowers have coloured and scented petals with a nectary at the base which produces sugary
nectar. Petals of this type attract insects which come to drink the nectar. As insects do this, they
transfer pollen from flower to flower.
Sepals: Many flowers have an outer ring of sepals. These often look like small green leaves.
Their function is to enclose and protect the flower when it is in the bud stage of development.
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A flowering plant's male sex cells are its pollen grains and its female sex cells are its ovules.
But neither type of sex cell is capable of movement. So how are the two brought together for
fertilization? The answer is that plants rely on pollen delivery services.
Pollination: The transfer of pollen from anthers to stigmas. This must occur before fertilization
can take place. Self-pollination is the transfer of pollen within the same flower, or between
flowers on the same plant and cross-pollination is the transfer of pollen between flowers on
different plants of the same type.
https://learn.genetics.utah.edu/content/flowers/pollinators/
https://learn.genetics.utah.edu/content/flowers/matchflowerpollinator/
Cross-pollination
Self-pollination
Wind-pollinated flowers:
Grasses and stinging nettles rely on wind to deliver pollen from flower
to flower. But the chances of a tiny pollen grain blowing straight from
the anthers of one flower to the stigmas of another even a short
distance away are very small indeed. However, wind-pollinated plants
have ways of overcoming these odds. First, they produce vast
quantities of light-weight pollen which floats on the slightest breeze.
Second, their flowers have spreading feathery stigmas which make a
large target for pollen grains to hit. Third, flowers and anthers are on
long stalks and so they are exposed to wind.
Insect-pollinated flowers:
Buttercups, peas, dandelions, and dead nettles are examples of the
enormous number of plants which make use of an extremely efficient
pollen delivery service: Insects. Insects do not carry pollen from flower
to flower free of charge. They are rewarded for their service in two
ways. First, they can eat some of the pollen itself and second, many
flowers produce nectar. Bees and butterflies find the sweet liquid so
attractive that they spend almost all their lives in search of it. Plants
advertise their pollen and nectar with brightly coloured flowers and scents which insects find
attractive. Often the brightest colours mark a path through the flower to where nectar is
produced. But as it follows this path an insect is either showered with pollen or brushed by
stigmas which pick up the pollen deposited on its body by another flower.
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Fertilization: Occurs after pollination. The nucleus of a pollen grain must fuse with the nucleus
of a female sex cell. This happens as follows. The pollen grain produces a long tube. This tube
grows down into the ovule. A nucleus travels down this tube into the ovule where it fuses with
the nucleus of the female sex cell.
After fertilisation: When the egg has been fertilised, the fertilised egg (zygote) divides
repeatedly and develops into an embryo. The embryo becomes surrounded by a hard wall. This
hard wall with the embryo inside is known as the seed. The seed contains a store of food,
usually starch. This will nourish the embryo later when it develops into a new plant. The final
stage in the formation of a seed is that it gets extremely dry, and in this state the embryo
becomes dormant. However, it is still alive and capable of developing into a new plant. It may
remain in this state for months or even years.
Fruits: The part of the flower surrounding the seed, or seeds, develops into the fruit. In most
plants the fruit is formed from the ovary which, after fertilization, may swell up considerably.
Dispersal of seeds: The job of the fruit is to help to carry the seeds as far as possible from the
parent plant. We call this process dispersal. This is important because if the seeds are not
dispersed, many germinating seedlings will grow very close to the parent plant. This results in
competition between every one of the seedlings as well as with the parent plant. The
competition is for light, space, water and nutrients.
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Fruits help to disperse their seeds in four main ways:
1. Some fruits are eaten by animals such as birds. The seeds are not digested but pass out
with the bird's droppings, often a long way from where the bird ate them. Many berry
seeds are dispersed this way. Fleshy fruits often look and taste nice, so animals are
attracted to them.
2. Some fruits disperse their seeds by splitting open. This may occur with such force that the
seeds are scattered quite a long way from the parent plant. Plants belonging to the bean
family have fruits of this sort: the 'pod' is the fruit, and the 'beans' are the seeds.
3. Some fruits are covered with little hooks which enable them to cling to the fur of animals,
thus aiding the dispersal of the seeds. A well-known example is the fruit of goosegrass
which clings to your clothes.
4. Some fruits have wings or hairs which slow their fall, allowing them to be carried away by
the wind. Sycamore trees have winged fruits, and dandelions have hairy parachutes.
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Watch the Flowering Episode of Private Life of Plants by David Attenborough
https://archive.org/details/ThePrivateLifeOfPlants_581/ThePrivateLifeOfPlants-03Flowering.wmv
CONNECT- How are the ideas
and information presented
CONNECTED to what you
already knew?
EXTEND- What new ideas did
CHALLENGE- What is
you get that EXTENDED or still CHALLENGING or confusing for
pushed your thinking in new
you to get your mind around? What
directions?
questions, wonderings or puzzles do
you now have?
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SEXUAL REPRODUCTIVE STRUCTURES IN FLOWERING
PLANTS PRACTICAL
This task requires you to gather information about the reproductive structures of flowering plants
using the following senses: touch, sight, and scent.
While you are identifying the different structures, enjoy the opportunity to learn through touching,
looking, and smelling. Be amazed by the delicate and intricate reproductive structures of a
flower!
Before you start, ensure you have the following equipment at your work bench:
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Flower
Magnifying glass
Scalpel
Tweezers
Tile
A4 white piece of paper
Investigation:
1. Looking at a typical flower. Detach a fully opened flower from the plant.
2. Refer to the diagram below.
3. Observe the flower without pulling it to pieces. You will see that it consists of a series of
rings of structures. Look for the sepals of your flower. The sepals are typically on the
outside of the flower. They are small green leaves round the outside of the flower.
4. Remove one of the sepals, how does it differ from an ordinary leaf?
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5. How does it differ from the petals?
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6. The petals compose the next “ring” of structures and are larger than the sepals. Examine
the texture and colour of the petals. Describe what you see and feel.
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7. Carefully remove two of the petals on one side of the flower.
8. This will enable your side of the flower more easily. Draw what you see.
9. The structures inside of a flower produce the gametes. The stamens each consist of a
stalk with a yellow knob at the end. Identify the stamens; they consist of an anther
supported by filament. Draw a stamen in the space below and label it.
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10. How many stamens do you see in your flower?
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11. The stamens each have an anther at the top of the filament shaft. Squeeze one of the
anthers with a pair of tweezers. Can you see any yellow specks? These are pollen grains.
The stamens are the male parts of the flower, and the pollen grains carry the male
gametes.
12. The carpel is a tall, column-like structure in the centre of the flower with a swollen base. It
consists of three parts: the stigma at the top, the style in the middle and ovary at the
base. Draw a carpel below.
13. The ovary contains ball-like ovules, each of which contains a microscopic egg. The carpel
is the female part of the flower. Using the scalpel, slice the ovary longitudinally.
Task 1: The picture below shows a certain flower viewed from above.
1. Name structure A – C.
A. _________________________
B. _________________________
C. _________________________
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2. What part of the flower:
a) protects the flower before the bud opens?
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b) contains an egg?
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c) is equivalent to an animal’s testis?
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d) contains the male gametes?
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Task 2: Brace map
Now that you are familiar with what the reproductive structures of the flower are and look like,
you need to understand what the function of each structure is in reproduction. Draw a Brace
map to show the components and subcomponents of a flower (they have been written in bold in
the investigation). List the function/s of each structure.
Remember to show that the stamen consists of the anther and the filament, and that the carpal
consists of the stigma, style, and ovary. Use a different colour to write the function next to each
structure.
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SEXUAL REPRODUCTION IN FLOWERING PLANTS
CONTINUED
Angiosperms are plants that produce flowers to reproduce sexually.
Flower Structure:
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All flowers have a basic structure as shown in the diagram below.
The flowers may differ between different species and between insect and wind-pollinated
flowers.
Function of the Flower:
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The flower is the organ of sexual reproduction. The function of the flower is to produce
gametes and to ensure that fertilisation takes place.
Many flowers produce both male and female gametes.
Flowers must ensure that pollination takes place.
Pollination:
Pollination is the transfer of pollen from the anther of the stamen to a stigma of the carpel.
There are two types of pollination:
Cross-pollination – the pollen is carried from the anther of one flower of one plant to the stigma
of the flower of another plant. This type of pollination results in genetic variation in the offspring.
Self-pollination – the pollen is carried from the anther to the stigma of the same flower or to
another flower on the same plant. This type of pollination will not result in genetic variation in the
offspring.
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Self-pollination is prevented by:
- Anthers and stigmas ripening at different times in bisexual flowers.
- Flowers being unisexual so that they cannot pollinate themselves.
- Stigmas positioned above the anthers.
Pollen is transferred either by insects or by wind. Plants are adapted structurally for the specific
agent of pollination:
Adaptations for Pollination:
Fertilisation:
Fertilisation is the fusing of the male gamete with the female gamete to form a zygote.
• After pollination has taken place, the pollen grain develops a pollen tube which grows
through the tissue of the style.
• When the pollen tube reaches the ovule in the ovary, it grows through a small opening in
the ovule called the micropyle, the tip of the pollen tube disintegrates, and the male
gamete enters the ovule.
• The male and female gametes fuse to form the diploid zygote, which will undergo mitosis
to form the new embryo.
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Seed Formation:
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The fertilised egg (zygote) divides several times to form the embryo.
The embryo develops a small root (radicle), a shoot (the plumule) and two seed leaves
(cotyledons).
The cotyledons are swollen with stored food.
The rest of the ovule develops into food storage tissue (the endosperm).
The outer covering of the ovule becomes thicker and tougher and forms a protective seed
coat (testa).
The ovary wall becomes the fruit which surrounds the seeds.
Fruit and Seed Dispersal:
Dispersal is essential to prevent overcrowding and competition between young plants. It also
allows a species to colonise new areas. There are four mechanisms of dispersal:
Animal dispersal:
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Fruit eaten or carried by an animal and deposited some distance away. Seeds may be
eaten with the flesh of the fruit and passed through the digestive system. The faeces
provide fertiliser for the germinating seed.
Many fruits have hooks which attach to fur of animals.
Wind dispersal:
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The fruit develops an outgrowth to increase surface area which allows the fruit to be
carried by wind.
These fruits are always very light.
Explosive dispersal:
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Seeds develop inside a fruit (pod) which dries out and splits into two. This splitting can
disperse seeds over a considerable distance.
Water dispersal:
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Waterborne fruits have air spaces within them to enable floating.
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Seed Germination:
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A seed will only germinate when it has the correct conditions.
Germination requires water, correct temperatures, and oxygen.
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LONGITUDINAL AND TRANSVERSE SECTIONS
In Biology we are often interested in the internal structure of organisms. This
means dissecting them and looking at the cut surface, often under a microscope. It is important
that you can work out where a section you are viewing has come from and how it relates to the
three-dimensional shape of the organism.
By the end of this lesson, you should be able to:
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Determine the plane along which a biological specimen has been cut (longitudinal or
transverse).
Visualise what the shape of the cut surface of a three-dimensional structure would be.
Identify the position in an organism from where a biological section has been taken.
Longitudinal and transverse sections
When 3-dimesnional biological specimens are cut into thin sections to view under a microscope
they are either cut along a longitudinal or transverse plane. The cut ends of the specimens
appear as different shapes, depending on the way in which they were cut.
When an object is cut lengthwise along the plane of symmetry, we refer to the cut surface as
a longitudinal section.
When an object is cut across or at right angles, we refer to the cut surface as a transverse
section.
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Terms for describing the architectural pattern of an organism
Dorsal: On or relating to the upper side or back of an animal, plant, or organ.
Ventral: On or relating to the underside of an animal or plant; abdominal.
Anterior: Nearer the front, especially in the front of the body, or nearer to the head or forepart.
Posterior: Further back in position; of or nearer the rear or hind end
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Longitudinal and transverse sections
worksheet
You will now make transverse and longitudinal section of a bean and two other items of your
choice from those provided. For each item you choose you will need to take two samples, one to
cut across and one to cut vertically along its length. When cutting a longitudinal section, you
must cut it in such a way as to get two similar (symmetrical) halves. It will not always be possible
to do this with a transverse section.
Draw the only the two-dimensional cut surfaces in the table below.
TRANSVERSE
LONGITUDINAL
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LOWER V BIOLOGY: SEED GERMINATION
Scientific Method
Often when we observe the world around us, we may make a ‘smart guess’ about the effect one
thing might have on another.
What we need to do to find out if we are right is to carry out an investigation.
We want to try to understand the world around us.
By understanding the world better, we can take better care of the world and ourselves.
Scientists ask questions: Why? Where? When? Who? What? Which?
Scientists use SCIENTIFIC METHOD to understand the things happening around them.
It is the process of thinking through the possible solutions to a problem and testing each
possibility to find the best solution.
The scientific process involves the following steps:
o Identify something that interests you and you would like to find out more about by
researching.
o Identify the specific problem and possible solution you want to test and formulate
an investigative question.
o Hypothesis and aim.
o Project experimentation.
o Project conclusion.
Throughout the process you are also continually redoing, improving, reassessing, and
researching.
Germination is the process by which a plant grows from a seed. Inside a seed is
an embryo, which is a tiny plant, and the endosperm, which provides food for the
embryo.
The outside of the seed has a coat, and this acts as protection for the embryo.
The embryo is safely stored inside the coat, waiting for the perfect time to begin
germinating.
Seeds need the right conditions to germinate, and, in some cases, they might have
to wait for years before those conditions are right.
Once the conditions are right, the plant inside starts to grow and get bigger. It
pushes open the seed coat, a bit like a chick hatching out of an egg. Tiny leaves
appear and they push out of the soil. The seed starts taking in water and gets
bigger and bigger until the coat splits apart. Air can then get to the seed. The
oxygen in the air helps the baby plant burn the food packed inside the seed. Using
the food produces energy. The baby plant uses the energy to grow. The root
begins to grow downward, and the baby stem begins to curl upward. Soon the
baby plant isn’t a baby anymore.
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RESEARCH:
Decide on the scientific question to be solved. It is best expressed as an “open-ended”
question, which is a question that is answered with a statement, not just a yes or no.
Do limit your problem. Do choose a problem that can be solved experimentally.
We are going to be investigating the effects of different factors on seed germination.
Our investigative question is:
Decide on a factor that will affect seed germination, i.e., (temperature, soil type, water, pH,
oxygen, etc.) and research more about it.
* Some things to consider:
1.
What type of seed are you going to use to conduct your investigation?
_____________________________________________________________
2.
How long does this seed that you have chosen usually to take to germinate?
_____________________________________________________________
Remember:
Seeds require water, oxygen and the correct temperature in order to germinate. These
requirements will affect the growth of your seeds and need to be kept the same to get
reliable results. These are called fixed variables and makes your experiment valid.
3.
Describe how will you ensure your seeds receive all these other factors in the same
quantities.
_____________________________________________________________
_____________________________________________________________
4 Provide the details of the experiment that you will conduct to determine which factor will
affect seed germination.
The variable that you are investigating and changing in a controlled manner
(it’s different in the separate experiments) – This is the independent variable.
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5 Write down the variable that you are going to measure or the outcome of the experiment.
This is the dependent variable. This variable changes during your experiment due to the
independent variable.
6 What is the aim of your experiment?
________________________________________________________________________
________________________________________________________________________
7 How will the variable you are testing (independent variable) affect the outcome?
(Dependent variable)? (i.e., predict the outcome of your experiment.). It doesn’t matter if
your prediction is right or wrong. It is a statement of what you may think may be correct,
but still need to test in an investigation.
________________________________________________________________________
________________________________________________________________________
8 List the materials that you think you would need to conduct the experiment:
Think
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•
•
•
about the following questions:
What exactly will be MEASURED in the experiment and
HOW will you measure it?
In what way could you make your measurements as
ACCURATE as possible?
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9 When writing a method for any investigation, it needs to be in point form
and set out in a logical sequence of steps that is easy to follow and
detailed enough that anyone else could follow your instructions and
repeat the experiment exactly. This makes the experiment RELIABLE.
The method needs to incorporate all the aspects you were asked to
consider on the previous pages regarding variables, measurement.
A list of apparatus is not required but must be mentioned the
appropriate equipment that should be used in carrying out each step or
making any measurements.
Sample size needs to be considered, as VALIDITY is increased by the
number of readings you take within range. This helps you calculate an
average with your data which makes your experiment ACCURATE.
Method is written in the third person.
Below is a method on how to grow an avocado tree.
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•
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•
•
•
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•
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Once you’ve finished your avocado, wash and dry the pit.
Fill a jar with water, almost to the brim.
Locate the broad end of the pit. This is the end that will
point down into the water.
Press three toothpicks around the pit. These will suspend
the pit from the rim of the jar. Place the toothpicks so
about one inch of the avocado pit is in the water.
Place the jar in a warm, sunny spot, but out of direct
sunlight. A windowsill is ideal.
Replenish water as needed.
Based on what you have just read on how to construct a method
for an investigation. Discuss why the method above is not suitable
for an investigation.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
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10. We are not going to carry out this experiment. Draw up a blank table in which
you record your results if you were to carry out the experiment. Remember
your tabulation rules.
11. Katy carried out an investigation to determine the correct soil for bean seeds to
germinate in. She used three different types of soil, sandy, silty loam and clay.
She planted one bean seed in each of the different soils. Once the seedling
sprouted from the soil, she measured the height of the seedling every day. After
three weeks she noticed that the tallest seedling grew out from the silty loam soil.
11.1 Write a conclusion for Katy’s experiment.
_________________________________________________________
_________________________________________________________
11.2 Katy’s experiment is flawed. Explain the experimental errors in her
process.
_________________________________________________________
_________________________________________________________
_________________________________________________________
_________________________________________________________
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SEXUAL REPRODUCTION IN HUMANS
HUMAN REPRODUCTION
CONNECT | EXTEND | CHALLENGE
https://www.youtube.com/watch?v=_5OvgQW6FG4&t=1s&ab_channel=NucleusMedicalMedia
CONNECT - How are the
ideas and information
presented
CONNECTED to what you
already knew?
EXTEND - What new ideas did CHALLENGE - What is still
you get that EXTENDED or CHALLENGING or confusing
pushed your thinking in new
for you to get your mind
directions?
around? What questions,
wonderings or puzzles do you
now have?
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Humans are complex multicellular organisms that can only reproduce sexually. This requires the
production of specialized sex cell or gametes which have half the number of chromosomes that
a normal body cell would have. Humans have 46 chromosomes. Cells in the reproductive
organs (ovaries in females and testes in males) undergo a special type of cell division called
meiosis to halve the number of chromosomes to 23 in the gametes. In the female ovaries the
gametes produced in this way are called eggs (ova) and in males the testes produce gametes
called sperm. When an egg and sperm fuse or join during fertilization the chromosome number
is restored to 46 and new gene combinations are formed. The cell that results is called a zygote
and it contains all the information necessary to make a unique human being.
Male reproductive organs:
Sperms are passed from a man to a woman by an organ called appends. When a man is
sexually stimulated spaces inside the penis fill with blood making it firm and erect. During
sexual intercourse the penis is placed inside the vagina. Muscular contractions in the sperm
tubes propel a liquid called semen into the female during ejaculation. Semen contains millions
of sperms together with chemicals which nourish them and cause them to begin swimming.
Female reproductive organs:
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During sexual intercourse the sperm from the male must swim from the female’s vagina, through
the cervical canal into the uterus. From here sperms must swim up the fallopian tubes to where
fertilisation occurs. Fertilisation can only occur if a fallopian tube contains an egg cell (ovum)
which has recently been released from the ovaries. A fertilized ovum moves down the fallopian
tube to the uterus where it develops into a baby.
Female periods and the menstrual cycle:
Fertilisation can only take place if an ovum is in a woman’s fallopian tubes when sexual
intercourse takes place. An ovum is released from an ovary once a month as part of a
sequence of events called the menstrual cycle. This sequence of events takes about 28 days
and is repeated continuously from the time a girl becomes sexually mature at puberty during the
teenage years until she is aged about 45 to 50. This cycle stops during pregnancy and starts
again soon after the baby is born.
Events during one menstrual cycle:
1. During the first 5 days of a cycle the uterus loses its lining. The lining breaks down
and passes out of the vagina as a quantity of blood. This is menstruation and it is
commonly known as a period.
2. Between the 13thand 15thdays one ovary releases an ovum. This is called
ovulation. The ovum travels slowly along the fallopian tube towards the uterus.
3. Between menstruation and the end of the cycle the uterus grows a new lining.
This lining consists of glands and blood vessels and is needed to nourish the ovum
in case it is fertilized and develops into a baby.
4. If the ovum is not fertilised menstruation begins again on or about day 28 of the
cycle.
Fertilisation and the start of development:
The first sperm to reach an ovum in the fallopian tube burrows into it so that the sperm’s nucleus
can fuse with the ovum’s nucleus to form a zygote.
The zygote begins to divide (by mitosis) and by the time it reaches the uterus it is a ball of cells
called an embryo.
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This ball becomes firmly embedded in the uterus wall. Here it receives food and oxygen from the
mother’s blood supply and grows into a foetus which is recognizable as a miniature human
being.
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HUMAN REPRODUCTION REVISION
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