ملخص Cells and Life العلوم منهج انجليزي الصف السادس
Lesson 1: Cells and Life
Revision Notes
Key Words
Cells — basic functioning unit of living things
Microscope — a deviæ used to magnify (make bigger) any specimen (object under observation)
Magnification — the number of times the object gets bigger under the micrcEcoFE (e.g. 1000x means the object gets bigger ICM) times)
Light microscope — a that uses light to see the specimen and has a lower magnification
Electron — a microscope that uses beam of electrons and has a higher magnification
Living things — include all forms of bacteria, fungi, protists, plants, and animals and have characteristics of life (MRSGREN)
Hierarchy — arrangement from Simple to complex
Unicellular — made up of one cell
Multicellular — made up of many cells
. Prokaryotic — cell without the nucleus and the genetic information (DNA) is freely floating on the cytoplasm
I I. Eukaryotic — cell where the DNA or the genetic formation is within the nucleus
. Homeostasis — ability to maintain constant tXdy conditions
. Stimuli — anything that causes a response
. External stimulu/stimuli — changes that outside the body and is passes to us through our sense organs (eyes, nose, ears, tongue, skin) e.g. levels of sunlight
. Internal stimuli — any change that happens within the body e.g changes in sugar levels
CHARACTERISTICS OF LIVING THINGS
For a living thing to be called living thing, it must possess certain characteristics
Such characteristics are
Movement
Respiration
Sensitivity
Homeostasis
Growth & Development
Reproduction
Excretion
Nutrition
1. Living things are organized
Living things are organized from simple to complex
• Organization starts from cells * tissues * organs * organ systems - orgamsm
2. Living things grow and develop
Living things grow and develop Growth refers to the increase in size
Development refers to the growth in mental and other skills
3. Living things reproduce
Reproduction is the ability to make offsprings similar to the parents
It can be sexual and asexual reproduction
4. Living things respond to stimuli
Stimuli are changes that happen either inside or outside the body that the living things have to respond to
Internal stimuli are changes that happen inside the human body such as hunger, changes in blood sugar levels etc
External stimuli are changes that happen outside the human body such as temperature, light levels, sound etc
Response is the result or the outcome of the stimulus
. Living things maintain internal conditions
Homeostasis is the ability to maintain stable intemal conditions
Humans need to maintain constant conditions such as: water levels, blood sugar, PH, temperature in order to survive
6. Living things use energy
• Living things need energy to survive
It can magnify up to 100,000 x the original Size of the Object
TYPES OF ELECTRON MICROSCOPE
1. Scanning Electron Microscope (SEM)
• Here the electrons pass the object and after reflected or bounce off the specimen to create a 3-D image
. Transmission Electron Microscope (TEM)
CELL THEORY
Robert Hooke
Here the electrons are transmitted or is absorbed by the object First person who investigated the cells using a cork stem Image of Robert Hooke "Cork" cells Anton van Leeuwenhoek
Made the microscope that iS more powerful than the one used by
Robert HOOke
He also studied cells from rain water and discovered animal cules
CELL THEORY
1. All thing things are made up of cells
. Living things are the basic functioning unit of life
. All cells come from pre-existing cells. (e.g. when we are wounded, the wounds heal
TYPES OF CELLS according to Number
I. Unicellular — only one cell, bacteria are the best example of unicellular organisms
. Multicellular — consists of many cells, cells of plants, animals, protists, and fungi are all multicellular
THREE BASIC PARTS OF THE CELL
f. Nucleus
2. Cytoplasm
the central part of the cell, the •control center" or the "brain" of the cell because it is the one that controls all the activities within the cell it contains the genetic information called the DNA that iS responsible for the traits that parents pass to the offspring
The fluid or the watery part of the cen This is where all the parts of the cell are found In the cytoplasm, all chemical reactions take place such as the photosynthesis and respiration
3. Cell Membrane
The outer part of the cell It is the one that controls what comes in and out of the cell (including oxygen, carbon dioxide, waster materials etc) It is like a security guard
TYPES OF CELLS ACCORDING TO THE LOCATION OF DNA
1. Prokaryotic
These are organisms that do not have nucleus but they do have the DNA or the genetic material
The genetic material or the DNA is not surrounded by the nucleus but it is located on the cytoplasm
Moreover, they do not have organelles (or parts)
They are typically smaller than eurkaryotes
• Bacteria are the example of prokaryotic
2. Eukaryotic
They have a definite nucleus where the DNA is found inside
They also have membrane - bound organelles
All forms of plants, animals, fungi and protist are eukaryote
CLASSIFICATION
All living things need to be classified
The biggest level of classification is the Domain
Kingdom is the next level of classification to Domain
There are three domains
Domain Archaea
Domain Bacteria
Domain Eukarya
There are Six Kingdoms of Living Things
Kingdom Archaea
Kingdom Bacteria
Kingdom Protista
Kingdom Fungi
Kingdom Plantae
Kingdom Animalia