GED Science Human Body and Health Summary

Sweat is mostly water. When it evaporates (turns into vapor) from the skin, it carries heat away from the body. This helps keep the inside of the body near a normal temperature. Keeping inside conditions steady is called homeostasis.

Wrong choices

• To raise the body's temperature: Sweating does the opposite. It lowers body temperature.
• To remove extra oxygen from the blood: Oxygen is not removed by sweat. Extra carbon dioxide leaves the body through the lungs.
• To store water in the skin for later: Sweating releases water from the body. It does not store water.

A vaccine shows the immune system a harmless form or part of a germ. The body learns to recognize that germ and can fight it quickly if the real germ enters later. This is why vaccination is a prevention method.

Wrong choices

• Taking antibiotics after symptoms start: Antibiotics are taken after an infection begins, and they work only on bacteria. They do not train the immune system ahead of time.
• Drinking more water each day: Drinking water is healthy, but it does not teach the immune system to recognize a germ.
• Wearing sunscreen outdoors: Sunscreen protects skin from ultraviolet light. It does not protect against germs.

Muscles are attached to bones. When a muscle contracts (gets shorter), it pulls on a bone, and the bone moves at a joint. So the muscular system and the skeletal system work together to move the body.

Wrong choices

• The respiratory system and the endocrine system: The respiratory system exchanges gases and the endocrine system makes hormones. Neither one pulls on bones.
• The immune system and the digestive system: The immune system fights germs and the digestive system breaks down food. They do not move the arm.
• The digestive system and the excretory system: These systems break down food and remove wastes. They do not move bones.

A bloodborne pathogen (germ) spreads when infected blood gets into another person's body, for example through a cut on the hand. Gloves put a barrier between the skin and the blood, so they are the best protection here.

Wrong choices

• Washing fruit before eating it: Washing fruit helps prevent foodborne illness. It has nothing to do with touching blood.
• Covering a cough with an elbow: Covering a cough stops germs spread by droplets in the air. It does not protect the hands from blood.
• Opening a window to let in fresh air: Fresh air helps with germs spread through the air. This germ spreads through blood, so touching the spill is the danger.

Carbohydrates (sugars and starches) are broken down into glucose. Cells use glucose for quick energy. Fats also supply energy, and protein can, but carbohydrates are the main fast source.

Wrong choices

• Vitamins: Vitamins help many body processes, but they contain no calories, so they do not supply energy.
• Minerals: Minerals such as calcium and iron are needed for bones and blood, but they do not supply energy.
• Water: Water is needed for life, but it contains no calories.

1. Fat: 10 × 9 = 90 Calories.
2. Carbohydrate: 20 × 4 = 80 Calories.
3. Protein: 5 × 4 = 20 Calories.
4. Total: 90 + 80 + 20 = 190 Calories.

Check: 190 − 90 − 80 = 20, which matches the protein.

Wrong choices

• 170 Calories: 170 is the total without the protein (90 + 80). The 5 grams of protein add 20 more.
• 140 Calories: 140 comes from using 4 Calories per gram for all 35 grams. Fat has 9 Calories per gram.
• 315 Calories: 315 comes from using 9 Calories per gram for all 35 grams. Only fat has 9.

In negative feedback, the body senses a change and responds in the opposite direction. Blood sugar goes up, so insulin is released to bring it down. This keeps the inside of the body steady, which is homeostasis.

Wrong choices

• a reflex controlled only by the spinal cord: Insulin is a hormone carried by the blood (the endocrine system). This is not a spinal cord reflex.
• positive feedback that pushes the change even further: Positive feedback makes a change bigger. Here insulin reverses the rise, so it is negative feedback.
• digestion of protein in the stomach: The pancreas is controlling blood sugar here, not digesting protein.

1. Mean before: (78 + 82 + 75 + 80 + 85) ÷ 5 = 400 ÷ 5 = 80.
2. Mean after: (72 + 76 + 70 + 74 + 78) ÷ 5 = 370 ÷ 5 = 74.
3. Decrease: 80 − 74 = 6 beats per minute.

Check: each volunteer's rate went down by 6 or 7, so a drop of 6 in the mean makes sense.

Wrong choices

• 8 beats per minute: 8 is the range of the after values (78 − 70), not the change in the mean.
• 10 beats per minute: 10 is the range of the before values (85 − 75), not the change in the mean.
• 74 beats per minute: 74 is the mean after walking, not the amount it went down.

The data show a pattern: more vaccination went with fewer cases. A good conclusion describes that pattern without claiming more than the data can show. Comparing only two towns cannot prove that one thing is the only cause.

Wrong choices

• The data prove that vaccination is the only reason Town A had fewer cases.: Two towns cannot prove a single cause. Other differences (age, crowding, travel) could also matter.
• The vaccine caused the extra cases in Town B.: Town B had fewer vaccinated people, so the data do not support the idea that the vaccine caused cases.
• Vaccination completely stops the disease from spreading.: Town A still had 2 cases per 10,000, so the disease was not completely stopped.

When the body is cold, blood vessels near the skin get narrower. Less warm blood reaches the surface, so less heat is lost to the cold water or air, and more heat stays in the core. Shivering is another response that makes heat.

Wrong choices

• Breathing stops until the body warms up: Breathing does not stop. The body still needs oxygen.
• Blood vessels in the skin widen, so more blood flows near the surface: Wider vessels near the skin would let more heat escape. This happens when the body is too hot, not too cold.
• The body sweats more to remove water: Sweating cools the body, which would make the problem worse.