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Summary natural science biology term 1 grade 9
mostly biology and a little bit of chemistry/physics
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Natural science: physics, chemistry, and biology Cell- the smallest unit of living organisms
Microscopic- something that is so small that it can only be seen when using a microscope.
DNA- the material found in cells that carries the hereditary information.
Organelle- specialised structures found inside living cells that perform specific functions for
the cell.
Cell membrane- the cell membrane forms the outer boundary of the cell; it surrounds the
contents of the cell.
Cytoplasm- cells are filled with a jelly-like substance called cytoplasm. It consists of water
with a complex collection of structures and materials that are either dissolved or suspended
in it.
Nucleus- all living cells contain DNA. In the simplest cells, such as bacteria, DNA occurs in the
cytoplasm. The nucleus is a round organelle surrounded by a nuclear membrane.
Organelles examples-
Mitochondria- are found in both plant and animals’ cells. Respiration takes place in the
mitochondria.
Vacuoles- are fluid-filled sacs that are surrounded by a membrane. They are used to store
substances which can then be used by the cell.
Chloroplasts- are only found in plant cells. Photosynthesis takes place in chloroplasts.
Chlorophyll- a green pigment found in chloroplast that gives plants their green colour.
Photosynthesis- the process by which plants use chlorophyll to convert radiant energy into
sugars.
System- a group of organs working together to perform a particular function.
Stimulus- a change in the environment which causes a reaction in a living organism.
Receptors- cells in sense organs which detect particular stimuli from the environment
Impulses- electrical signals transmitted along nerves.
Nerve cells- cells that receive and send messages in the form of a week electrical current
from the body to the brain and back to the body.
Spinal cord- a cord of nerve tissue that extends from the brain through the spinal column in
which the nerve cells carry information from the body to the brain and back to the body.
Nervous system-
Function- the nervous system receives and helps the body respond to stimuli.
Structure- the main components of the human nervous system include the brain, spinal cord, nerves,
ears, nose, eyes, skin, and tongue.
Main processes- the main processes include hearing, seeing, feeling, tasting, smelling, sending, and
receiving impulses and regulating temperature.
Ovaries- female sex organs where egg cells are produced.
Testes- male sex organs where sperm cells are produced.
Uterus- place where the baby grows.
Reproductive system-
Function- the reproductive system produces sex cells for the purpose of continuing the species.
,Structure- the main components of the human reproductive system include the testes, ovaries, and
the uterus. Men have the testes that produce sperm cells which are the male sex cells. Women have
ovaries that produce egg cells which are the female sex cells.
Main processes- the main processes include copulation, ejaculation, ovulation. Menstruation,
fertilisation and implantation, growth, cell division and maturation.
Purpose and puberty-
Purpose of reproduction-
Reproduction means to make more organisms or living things. All living things including animals and
plants reproduce to make more individuals of the same type of species.
Extinct- a species has died out completely and there are no living members left.
Offspring- the young produced by an organism
Gametes- the sex cells also called sperm cells and egg cells
Fertilisation- fusion of the egg and the sperm
Embryo- early development stage
Genetic information- inherited information that is passed on from parents to the young
Asexual reproduction-
In asexual reproduction there is only one parent. The offspring are identical to the parent.
Sexual reproduction-
Humans reproduce by sexual reproduction. In sexual reproduction there are two parents. The
parents have reproductive organs that have sex cells or gametes. The sex cells or gametes are also
called sperm cells and egg cells. The testes are the male reproductive organs, which make sperm.
The female ovaries are the reproductive organs, which produce egg cells. A new life starts when an
egg cell and a sperm cell join during fertilisation. The fertilised egg cell divides to form a ball of cells.
It becomes the embryo and will eventually develop into a new individual.
Puberty-
Puberty- stage in the human life cycle when the sexual organs mature for reproduction.
Pituitary gland- structure found at the base of the brain which starts to make hormones.
Hormones- chemicals that are made by glands, and they speed up or slow down the
activities of an organ.
Secondary sexual characteristics- changes in the bodies of males and females that happen
during puberty.
Emotional changes-
During puberty you may also experience changes in your emotions. Emotions are strong feelings
about something or somebody. These changes can have emotional and psychological effects such as
unexplained mood changes, low self-esteem, aggression, and depression.
, Reproductive organs-
Male reproductive organs-
The male reproductive organs include the penis, sperm duct (vas deferens), testes, scrotum, and
urethra. FUNCTIONS:
1. Make and store sperm and
2. Place sperm in the female
The path of a sperm-
The production of sperm I the testes during puberty. Sperm travels from the testes along the sperm
duct. as it moves through the sperm duct it is mixed with fluids from the male glands. The mixture is
called semen. The semen moves through the urethra which runs through the penis.
Female reproductive organs-
The female reproductive organs include the vagina, uterus, ovaries, and the oviducts (fallopian
tubes). FUNCTIONS:
1. Make egg cells, and
2. Provide suitable conditions for the growth of a baby
The path of the egg-
Each month, one egg is released from one of the ovaries. The egg travels from the ovary
along the oviduct to the uterus. The egg cannot move on its own and swept along the
oviduct by the action of tiny hairs.
Stages of reproduction-
Copulation- the process where the erect penis is placed in the vagina.
Ovulation- the release of a ripe egg from the ovary
Menstruation- the breakdown of the lining of the uterus that contains many bloods vessels
Menstrual cycle- a series of changes that happen in the female reproductive organs
Ovulation-The release of a ripe egg from the ovary.
Copulation- the process where the erect penis is placed in the vagina.
Menstruation- the breakdown of the lining of the uterus that contains many bloods
vessels
Menstrual cycle- a series of changes that happen in the female reproductive organs
Fertile period-
A woman is only likely to fall pregnant on a few days during her menstrual cycle. The period last
between 4-7 days.
Zygote- fertilised egg
Implantation- embryo sinks into the lining of the uterus that contains many blood vessels.
Foetus- the human embryo after eight weeks of development.
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