Science Flashcards
What is variation?
the differences that occur between different species and within the same species
What is variation caused by?
genetics and the environment
What are inherited variations?
these are inherited characteristics from parents e.g. facial features, height, hair colour, eye colour
What are environmental variations?
traits that are influenced by the environment e.g. hair length, language, strength
Do you think skin colour is an inherited or environmental characteristic?
Both - a child will have similar skin colour to its parents, but it can change with sun exposure
What are the 4 features that are truly inherited (and not affected by the environment)?
natural eye colour
natural hair colour
blood group
inherited disease
Most features are caused by both inherited and environmental factors, true or false?
True
What is continuous variation?
a feature that can take on any value in a range e.g. height can be anything from the smallest human possible to the tallest human possible
What is discontinuous variation?
a feature that can only have certain values e.g. eye colour can only be brown. blue or green. Another example is blood type
True or false - identical twins are genetically identical
True - identical twins come from a single egg and sperm
Do non-identical twins come from the same egg?
No - they come from 2 separate eggs fertilized by different sperm
What makes organisms different from each other?
DNA - DNA is unique to that organism. Except for identical twins, they have identical DNA
Where is DNA located?
at the nucleus of cells and they are tightly coiled into packages called chromosomes
What is a gene?
a particular section of DNA
How many chromosomes do humans have?
most human body cells contain 46 chromosomes - they are matched up as 23 pairs
Who do people inherit chromosomes from?
half from mother, half from father
What does a gene control?
separate characteristics e.g. eye colour
What do proteins do?
they perform many roles in the body
What type of protein forms cells and tissues?
Structural protein
What type of protein carries out reactions in the body?
functional proteins
Give 2 examples of structural proteins
collagen (found in many human tissues)
cellulose (found in plant cells)
Give an example of a functional protein
Enzymes
What do enzymes do?
they catalyze (cause) reactions
We may look similar to our parents, but our characteristics will not be exactly the same. Why?
- Because when sex cells are produced (gametes), genes are swapped between the chromosomes so that they are not the same as the parent cell
- At fertilisation, any sperm could fuse with the egg, mixing the genes from both parents
We may look similar to our parents, but our characteristics will not be exactly the same. What is this called?
genetic variation
What is another cause of genetic variation?
mutation
What is a mutation?
where there is a change in the type or amount of DNA
When do mutations occur?
- When DNA is not copied correctly during replication
- when chromosome pairs divide unequally during cell division
Give some examples of mutations that can be caused by environmental factors
- radiation, such as UV radiation
- exposure to certain chemicals
(these factors are called mutagens)
Is body mass (your weight) determined by genes or the environment?
both - it is inherited but is also affected by how much you eat and exercise
What must occur for a woman to become pregnant?
fertilisation
What is fertilisation?
The fusing of an egg and a sperm cell. The sperm’s nucleus will join the egg’s nucleus
How often do females produce an egg?
approximately every 28 days
What is ovulation?
When a female produces an egg (every 28 days)
How often do males produce sperm in the testes?
continually
What are the 5 stages of fertilisation?
1 - ovulation (egg is released from the ovary)
2 - sperm is released into the vagina and travels to the oviduct
3 - the nucleus of a sperm and egg fuse together to produce a zygote
4 - the fertilised egg travels to the uterus and embeds itself into the lining
5 - the fertilised egg is now called an embryo - the lining of the uterus develops into the placenta for nourishing the embryo into a fetus
What is the name given to a male gamete?
Sperm
Where does the female egg cell implant after fertilisation?
Uterus lining
True or false - there is no mixing of maternal and fetal blood in the placenta
True
Where does fertilisation occur?
In the Oviduct
True or False - egg cells have a tail?
False
What is the name given to a female gamete?
Egg cell
Which substance can diffuse across the placenta from mother to fetus?
Glucose
What is a zygote?
A fertilised egg cell before it has divided into an embryo
What is the placenta?
an organ that grows into the wall of the uterus and is joined to the fetus by an umbilical cord
What does the placenta do?
allows the exchange of oxygen and nutrients (such as glucose) between the fetus and mother and removes waste such as carbon dioxide and urea
How does the placenta exchange materials between the fetus and mother?
by diffusion
What are the 2 functions of the ovaries?
- contain eggs
- make female hormones which affect the way the body develops and regulates menstrual cycle
How long does it take for a fetus to develop and what is this time called?
40 weeks, gestation period
What happens during birth?
the cervix relaxes and the muscles in the wall of the uterus contract. Waves of muscle contractions push the baby out of the vagina
which part of the female reproductive system is immediately above the vagina?
the cervix
Which part of the male reproductive system holds the testes?
the scrotum
Which terms describes the time between pregnancy and birth?
Gestation
When an egg cell joins a sperm this is called..
fertilisation
A fertilised egg divides to form a ball of cells called…
An embryo
Which substances does not move through the placenta to the fetus:
- nutrients
- oxygen
- carbon dioxide
Carbon dioxide
What is the role of the testes?
they produce sperm and the hormone testosterone
Which tube carries urine out of the body in the male and female reproductive systems?
the urethra
What is photosynthesis?
Plants make their own food using photosynthesis. They do this by producing glucose and oxygen from carbon dioxide and water
What is the word equation for photosynthesis?
Carbon dioxide + Water (then chlorophyll absorbs light) = Glucose + Oxygen
What type of reaction is photosynthesis?
Endothermic
What is chlorophyll?
the green chemical inside the chloroplasts of plant cells
What does chlorophyll do and where is it located?
It is in the leaves and it absorbs light
How does carbon dioxide enter the plant for photosynthesis?
carbon dioxide comes from the air and it enters the leaves through the stomata
How does water enter the plant?
Through the roots
What happens to the oxygen and glucose made during photosynthesis?
the plant releases oxygen into the air, glucose is used to make cell walls and makes the plant grow
What does a plant need for photosynthesis to happen?
- Water
- Carbon dioxide
- light
How does light affect photosynthesis?
Without enough light, a plant cannot photosynthesise very quickly - even if there is plenty of water and carbon dioxide
What is selective breeding in plants?
An artificial process in which humans choose the characteristics to grow e.g. for crops
How does selective breeding happen?
Humans choose the best plants to breed together to produce the next crop, they repeat this process over many generations to get the desired plant (can also be done for cattle to produce the best meat)
What types of plants do humans choose for selective breeding?
- disease resistant crops
- wheat plants that produce lots of grain
- large or unusual flowers
What types of animals do humans choose for selective breeding?
- animals that produce lots of milk or meat
- chickens that lay large eggs
What are the benefits of selective breeding?
can produce more or better quality food
What are the risks of selective breeding?
- reduced genetic variation which can lead to specific problems e.g. can lead to attack by insects (for plants), or in animals it can create physical problems like deafness or bad hips in dogs
What is a pH scale?
Used to measure acidity and alkalinity
What can chemicals be classified as in a pH scale?
Acid
Neutral
Alkaline
What does an acid form when it is neutralised?
a salt
What are pH indicators?
They are substances that change colour when they are added to acidic or alkaline solutions
What type of solution has a pH scale of less than 7?
Acidic
What type of solution has a pH of 7?
Neutral
What type of solution has a pH scale greater than 7?
Alkaline
What colour does a universal indicator change to for a strong acid?
Red
What colour does a universal indicator change to for a weak acid?
Yellow or orange
What colour does a universal indicator change to for a neutral solution?
green
What colour does a universal indicator change to for a strong alkaline?
dark blue
What colour does a universal indicator change to for a weak alkaline?
light blue
When an acid is dissolved in water what does it produce?
Hydrogen ions (protons)
When alkalis are dissolved in water what do they produce?
hydroxide ions
What is a base?
chemical opposite of an acid
What happens when an acid is mixed with an alkaline
a neutralisation reaction occurs to form water
Which of the following could have a pH of 12?:
- Sodium Chloride
- Sulfuric acid
- Sodium Hydroxide
Sodium Hydroxide
What is neutralisation?
when an acid reacts with a base or alkali to form salt and water
What is rust?
when a metal object (like Iron) is exposed to open air and bad weather it corrodes
What causes rust?
Air
Moisture
Salt water
How can rust be prevented?
Can stop air and water reaching the metal by:
- painting it
- greasing it
- covering it in a more reactive metal e.g. with zinc (galvanise)
- covering it in a less reactive metal e.g. gold, silver (electroplating)
What are the indicators that a chemical reaction has taken place?
- a change of colour
- a change of temperature
- the production of a gas or solid (effervescence / precipitation)
What affects the rate (speed) of a chemical reaction?
- temperature
- concentration
- particle size
- presence of a catalyst
What is a chemical reaction?
When one or more substances change and produce one or more new chemical substances
What are the substances that are changed by a chemical reaction called?
Reactants
What are the substances that are produced by a chemical reaction called?
products
A colour change might take place when two substances react. It can also happen when a compound is broken down by heating it. What is this called?
Thermal decomposition
Effervescence is an indicator that a chemical reaction has taken place. How does this show in a liquid?
Bubbles of gas in the liquid