Biology Term 1
Unit 1 – Cells
B1.1
B1.1 TB
The largest known living single-celled organisms are sponge-like creatures called xenophyophores that live on the ocean floor. They can reach a size of up to 20 cm across.
The biggest egg ever laid was about 30 cm in length and was laid by an animal that is now extinct: the Elephant Bird of Madagascar.
B1.3
Eyepiece / Objective / Magnification10 / 10 / 100
15 / 100 / 1500
5 / 20 / 100
10 / 40 / 400
B1.5
Specialised human cells include red blood cells, white blood cells, muscle cells, brain cells, sex cells (gametes), liver cells, skin cells.
In a flowering plant, specialised cells include root hair cells, leaf cells, gametes (sex cells) and palisade cells.
B1.6
Excretory system: liver, kidneys
Nervous system: brain
Digestive system: stomach, intestines
B1.7
Unit 2 – Size matters
B2.1
Each side is a square so:
Surface area of each square = 4 cm ´ 4 cm
= 16 cm2
Total surface area of cube = 16 ´ 6 = 96 cm2
Volume of cube = 4 cm ´ 4 cm ´ 4 cm = 64 cm3
So the surface area to volume ratio = 96/64 = 1.5
B2.2
A mouse has fur over its body and face to keep heat in. It also sits very close to the ground and can roll up into a ball to keep heat in.
B2.3
Large organisms need much more energy to live than small organisms, so they have larger and more complicated digestive systems. They need big, powerful hearts to pump the blood around their circulatory systems.
B2.3 TB
A small bird such as a hummingbird has feathers to keep warm and to help it fly. It flies short distances and has to flap its wings very fast. Its heart is small and beats very fast to keep circulating its blood. It spends most of the daytime finding food, and eats higher energy food such as nectar. Many small birds huddle together in groups at night to share warmth.
A small mammal such as a bat lives and sleeps during the day huddled together with many other bats to keep warm. It lives in warmer, sheltered, dark places out of reach of predators. Its wings are made of skin that it wan wrap around itself to keep warm; its body is covered in fur. It spends most of the night flying fast and catching and eating insects. Bats hibernate over the winter to avoid cold temperatures and lack of food.
A small reptile such as a lizard seeks out warm, sunny places in which to spend the day. Lizards are cold-blooded, meaning they need external warmth such as from the Sun in order to live. When they need to move they do so quickly, in order to catch prey such as insects.
B2.4 TB (1)
Total volume of lungs is about 6000 cm3. There are 10 mm in every 1 cm, so there are 1000 mm3 in every 1 cm3. So the total volume of lungs is about 6000 ´ 1000 = 6000 000 mm3
B2.4 TB (2)
B2.4 TB (3)
Total surface area = area of one alveolus ´ number of alveoli = 0.2 mm2 ´ 750 000 000
= 150 000 000 mm2 = 1500 000 cm2
B2.4 TB (4)
Total surface area of lungs if they were simple spheres = 2000 cm3. So by having millions of alveoli inside the lungs, the total surface area = = 750 times larger than simple spheres.
B2.4 TB (5)
Surface area of tennis court = 23.2 ´ 8.2 = just over 190 m2 = 1900 000 cm2. So the surface area of the alveoli in our lungs is not much smaller than the area of a tennis court!
B2.5
A blue whale’s brain is the largest brain known. It has a mass of about 6.0 kg, which is slightly more than four times more massive than a human brain. This might mean blue whales are very intelligent, but we know that the size of an animal’s brain does not necessarily relate to the animal’s intelligence. (We know that whales communicate through complex sounds and show intelligent behaviour, but we cannot tell how intelligent they may be from the size of their brains.)
Unit 9 – Movement
B9.1
A sensitive plant detects an object nearby by a change in the electrical charge on the leaves. The leaves then fold up, and the leaf stalks droop down, because the plant withdraws water from the leaves and stalk.
B9.2
Bones have blood vessels because the living cells in bone need a supply of nutrients. Also, the new blood cells formed in the bone marrow need to be carried away to join the rest of the blood in the body.
B9.5
The thigh contains an antagonistic pair of muscles, one in the front and one behind the bone. (There are more muscles than this in the thigh, but this explains the basic principle.) To lift the leg up, the front muscle contracts while the back muscle relaxes; to push the leg back down, the front muscle relaxes and the back muscle contracts.
B9.5 TB
What appears to be a ‘knee’ on a flamingo is in fact the equivalent of a human ankle. The flamingo’s knee is hidden under its feathers, higher up near the top of its leg.
B9.6 (1)
Bones help protect your organs from damage, as well as hold the parts of our body in place and make blood. If you are playing sports, you can protect your bones from damage by wearing protective clothing and being careful. If you are unlucky enough to break a bone, if it did not repair itself you would lose protection of your organs in that part of your body, and you might not be able to walk (if, for example, a leg bone stays broken).
B9.6 (2)
Fruit and vegetables provide minerals and vitamins. We can get minerals and some vitamins from dairy products too such as milk.