Term
| How does natural selection happen? |
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Definition
- Living organisms produce many offspring.
- The offspring vary from one another, because they have differences in their genes.
- Some of them have genes that give them a better chance of survival. They are most likely to reproduce.
- Their genes will be passed on to their offspring.
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Term
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Definition
| Occasionally, unpredictable changes to chromosomes and genes happen. These are called mutations. |
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Term
| How have some forms of bacteria become resistant to antibiotics? |
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Definition
This happened as a result of mutation in the bacteria producing a form of a gene that helped them survive, even when the antibiotic was present in their enviroment.
This was just chance. The bacteria did not purposefully mutate to become resistant. |
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Term
| What are the different parts of a cell called? |
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Definition
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Term
| What organelles do animal cells have? |
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Definition
- Ribosomes
- Mitochondria
- Cytoplasm
- Cell membrane
- Nucleus
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Term
| What organelles do plant cells have? |
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Definition
- Cell membrane
- Ribosomes
- Cytoplasm
- Mitochondria
- Cell Wall
- Chloroplasts
- Vacuole
- Nucleus
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Term
| What organelles do ONLY PLANT cells have? |
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Definition
- Cell wall
- Chloroplast
- Vacuole
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Term
| What is cell membrane and what is it for? |
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Definition
| The cell membrane is a thin semi-permeable membrane that surrounds the cytoplasm of a cell, enclosing its contents. Its function is to protect the quality of the interior of the cell by allowing certain substances into the cell, while keeping other substances out. |
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Term
| What are ribosomes and what are they for? |
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Definition
| Tiny structures within a cell, where protein synthesis takes place. |
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Term
| What is mitochondria and what is it for? |
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Definition
Organelle where energy is released in aerobic respiration.
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Term
| What is cytoplasm and what is it for? |
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Definition
| The jelly-like material that fills the inside of a cell, in which metabolic reactions take place. |
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Term
| What is the nucleus and what is it for? |
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Definition
| Contains the chromosomes made of DNA, and which controls the activities of the cell. |
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Term
| What is a cell wall and what is it for? |
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Definition
| A strong covering made of cellulose, found on the outside of plant cells. |
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Term
| What is a chloroplast and what is it for? |
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Definition
| Organelles found in plant cells that absorbs energy from sunlight. |
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Term
| What is a vacuole and what is it for? |
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Definition
| Liquid-filled space inside - many plant cells contain vacuoles full of cell sap. |
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Term
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Definition
| When a cell splits in two to create more cells. |
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Term
| Why is mitosis important? |
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Definition
| Because it provides cells for growth and replaces dead or damaged cells. |
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Term
| How many pairs of chromosomes do normal body cells have? |
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Definition
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Term
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Definition
- Chromosomes are copied and line up along the middle of the cell.
- The identical copies of each chromosome split apart and move to opposite end of the cell.
- The chromosomes now form into two nuclei.
- New cell membranes form and two new cells have been made.
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Term
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Definition
- Before meiosis begins, each chromosome is copied exactly. The two copies stay attached to one another.
- Each chromosome finds its partner from the other set.
- The chromosomes seperate from their partners, and the cell divides.
- Each cell divides again, this time seperating the two copies of each chromosome.
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Term
| What are the differences between meiosis and mitosis? |
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Definition
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Mitosis
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Meiosis
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The cell divides once.
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The cell divides twice.
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Two cells are made.
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Four cells are made.
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The new cells have the same number of chromosomes as the original cell.
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The new cells have half the number of chromosomes as the original cell.
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This is how new body cells are made.
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This is how gametes (sex cells) are made.
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It happens in all parts of the body.
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It only happens in the testes and ovaries.
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Term
| What is a specialised cell? |
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Definition
| A cell with a very specific job to do in the human body. |
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Term
| Examples of specialised cells? |
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Definition
- Bone cells
- Muscle cells
- Heart cells
- Brain cells
- Red blood cells
- Goblet cells
- Cilated cells
- Nerve cells
- Sperm cells
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Term
| How many specialised cells are there in the body? |
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Definition
| There are over 200 types of specialised cells in the human body. |
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Term
| Example of a specialised cell that plants have? |
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Definition
| Root-hair cells - They are fine hair-lik extensions of a root. Their large surface area enables plants to maximise their absorption of water from the soil. |
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Term
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Definition
Yeast is a single-celled fungus. Its cells have cell walls but they are not made of cellulose like plant cell walls. Fungi cannot photosynthesise and they have no chloroplasts.
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Term
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Definition
| Algae are simple, plant-like organisms. Their cells are similar to plant cells. |
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Term
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Definition
| Bacteria does not have a nucleus. Their genes are in the cytoplasm. |
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Term
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Definition
| Viruses are not made of cells. They do not have cell membranes, cytoplasm or a nucleus. Most viruses are made of a sphere of protein, with some DNA inside it. They are hundreds of times smaller than a cell. |
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Term
| What are the three limiting factors? |
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Definition
- Light - may be due to lack of carbon dioxide and/or the temperature is too low/high
- Carbon dioxide - may be due to lack of light and/or the temperature is too low/high
- Temperature - may be due to lack of light and/or lack of carbon dioxide
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Term
| What is the equation for photosynthesis? |
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Definition
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Term
| How do plants use glucose? |
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Definition
- Converted into starch molecules for storage
- Used for respiration
- Converted into fats and oils for storage
- Used to produce cellulose which strengthens cell walls
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Term
| What factors must be controlled in a greenhouse to improve plant growth/photosynthesis? |
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Definition
- Temperature
- Availability of nutrients
- Amount of light
- Availability of water
- Availaility of oxygen
- Availability of carbon dioxide
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Term
Question on diagram:
Both cells are drawn the same length, but the magnification of each cell is different. Cell A is magnified x 50,000, and Cell B is magnified x 500. The real length of Cell A is 2 micrometres. How would you calculate the real length, x, of Cell B? Also show answer. |
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Definition
(Known length of Cell A times magnification of Cell A) divided by magnification of Cell B
=
Answer!
so
(2 micrometres X 50,000) / 500
or
100,000 / 500
=
x = 100 micrometres |
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Term
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Definition
| Osmosis is the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane. It is a type of diffusion, but it is only the movement of water molecules. |
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Term
| What are partially permeable membranes and what do they do? |
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Definition
| They let through small molecules like water, but not larger molecules like glucose. Examples include visking tubing and cell membranes. |
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Term
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Definition
Basically a blank cell that has the potential to develop into any kind of cell in the human body.
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Term
| Where do stem cells come from? |
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Definition
| In animals, the fertilised egg divides over and over again to produce an embryo. For the first few days, all of these cells stay as stem cells. |
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Term
| What happens to these cells? |
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Definition
| Most cells differentiate and form specialised cells. A few remain as stem cells and can continue to divide and specialise throughout adult life. |
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Term
| What can stem cells be used for? |
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Definition
| Stem cells from embryos and adults (particularly bone marrow stem cells) coulld be used to replace damaged tissues in the future. |
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Term
| What is a plant covered in and what is it for? |
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Definition
The whole plant is covered in a layer of epidermis.
This helps:
- To protect the underlying cells.
- Stop the leaves from losing too much water.
- Prevent pathogens from entering the plant.
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Term
| What are organs in a plant made up of? |
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Definition
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Term
| What are most of the cells in a leaf? |
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Definition
| Mesophyll cells. This is where photosynthesis takes place. |
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Term
| What runs through the entire plant? |
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Definition
| Xylem and phloem tubes. These make up the plant's transport system. |
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Term
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Definition
| Carry water from the roots to the leaves. |
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Term
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Definition
| Transport sugars around the plant. |
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