AQA Biology Unit 1 Revision

White blood cells play a crucial role in protecting the body against diseases. They are a part of the immune system and are responsible for identifying and attacking foreign substances such as bacteria, viruses, and other pathogens. They help in preventing infections and maintaining overall health by producing antibodies and destroying harmful invaders. Therefore, the statement "protect the body against diseases" accurately describes the role of white blood cells.

LSD is considered illegal because it is a hallucinogenic drug that alters perception and can cause intense hallucinations and distortions of reality. It is classified as a Schedule I controlled substance in many countries, including the United States, meaning it has a high potential for abuse and no accepted medical use. The use and possession of LSD are prohibited by law, making it illegal to possess, sell, or distribute.

Animals such as polar bears keep their surface area to volume ratio as small as possible to keep body heat. This is because a smaller surface area compared to their volume reduces heat loss to the environment. In cold environments like the Arctic, where polar bears live, maintaining body heat is crucial for survival. By minimizing their surface area, polar bears can conserve heat and stay warm in their icy habitat.

Cloned animals are created by the process of somatic cell nuclear transfer, where the DNA from a donor animal is inserted into an egg cell and then implanted into a surrogate mother. This process results in an animal that is genetically identical to the donor animal, as it carries the same DNA. Therefore, the statement that cloned animals are genetically identical is true.

Asexual reproduction refers to the process of reproduction where only one parent is involved, and there is no need for the participation of another partner. This means that a single organism can reproduce and produce offspring without the need for sexual reproduction or the involvement of another individual. Therefore, the statement "Asexual reproduction requires only one partner" is true as it accurately describes the nature of asexual reproduction.

A mutated virus can cause an epidemic as it refers to a virus that has undergone genetic changes, resulting in a new strain that may be more contagious or virulent. These mutations can enable the virus to spread rapidly within a population, leading to a widespread outbreak or epidemic. The mutation may affect the virus's ability to evade the immune system or its transmission capabilities, allowing it to infect a larger number of individuals and cause a significant public health crisis.

Cacti actually lose less water than trees. This is because cacti have adapted to dry environments and have developed thick, waxy skin and spines to reduce water loss through evaporation. They also have shallow roots to absorb water quickly when it rains. On the other hand, trees have a larger surface area for water evaporation and deeper roots that require more water to survive. Therefore, the statement that a cactus loses more water than a tree is false.

Alexander Fleming did discover penicillin. In 1928, he noticed that a mold called Penicillium notatum was inhibiting the growth of bacteria on a petri dish. This accidental discovery led to the development of the first antibiotic, penicillin, which revolutionized medicine by effectively treating bacterial infections. Fleming's work on penicillin earned him a Nobel Prize in 1945 and established him as one of the most important figures in the history of medicine.

Synapses are the junctions between nerve cells that allow for communication between them. When an electrical signal reaches the end of a nerve cell, it triggers the release of chemicals called neurotransmitters into the synapse. These neurotransmitters then bind to receptors on the neighboring nerve cell, transmitting the signal and allowing for the continuation of the electrical impulse. Therefore, it is true that synapses release chemicals.

Nerves are not directly joined together. They are part of the nervous system, which consists of a complex network of nerves that transmit signals between different parts of the body. Nerves are made up of individual nerve cells called neurons, which are connected to each other through synapses. These synapses allow for the transmission of electrical signals between neurons, enabling communication within the nervous system. Therefore, nerves are not directly joined together but rather connected through synapses.

An adult cell is a type of cloning because it can be used in the process of somatic cell nuclear transfer (SCNT) to create a genetically identical organism. In SCNT, the nucleus of an adult cell is transferred into an egg cell that has had its nucleus removed, and then the egg cell is stimulated to develop into an embryo. This technique has been used to clone animals such as Dolly the sheep.

The correct order of a reflex arc is stimulus, receptor, coordinator, effector, and response. In a reflex arc, a stimulus is detected by a receptor, which then sends a signal to a coordinator (usually the central nervous system). The coordinator processes the information and sends a signal to an effector, which carries out the appropriate response. Therefore, the correct order is stimulus receptor coordinator effector response.

A Saguaro cactus loses less than one glass of water in the desert in one day. This is because the cactus has adapted to survive in arid conditions by minimizing water loss. It has a thick waxy skin that reduces evaporation, and its spines help to shade and protect the plant from excessive heat. The cactus also has a shallow but extensive root system that allows it to quickly absorb any available water. Overall, the Saguaro cactus is highly efficient in conserving water, enabling it to survive in the desert with minimal water loss.

The liver is responsible for detoxifying harmful substances that enter the body. It filters and processes toxins, drugs, and alcohol, converting them into less harmful substances that can be eliminated from the body. This process helps protect other organs and tissues from damage caused by these toxins. Therefore, it can be concluded that the liver deals with all the poisons that enter the body, making the statement true.

The statement "Animals compete for three things: water, territory and light" is not correct. While animals may compete for resources such as food and mates, the specific things mentioned in the statement (water, territory, and light) do not encompass all the factors that animals compete for. Therefore, the correct answer is False.

LDL stands for low-density lipoprotein, which is commonly referred to as "bad" cholesterol. This is because high levels of LDL in the blood can lead to the buildup of plaque in the arteries, increasing the risk of heart disease and stroke. Therefore, it is important to keep LDL levels low to maintain good cardiovascular health.

The equation for BMI is calculated by dividing the weight of an individual by the square of their height. This is because BMI is a measure of body fat based on weight and height. By dividing weight by height squared, we get a standardized value that can be used to assess whether an individual is underweight, normal weight, overweight, or obese.

The given statement suggests that almost everyone who uses cannabis eventually progresses to using heroin. This implies that cannabis use is a gateway drug that leads to the use of more dangerous substances. However, it is important to note that this statement is not supported by scientific evidence and is a common misconception. While some individuals may experiment with different drugs, there is no direct causal relationship between cannabis use and heroin use. Drug use patterns vary greatly among individuals, and it is inaccurate to make a blanket statement that everyone who uses cannabis will eventually use heroin.

The correct answer is "centra nervous system". However, this answer is incorrect as there is no such term as "centra nervous system". The correct term is "central nervous system" (CNS), which refers to the complex of nerves and tissues that control and coordinate the activities of the body.

Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose. Cellular respiration, on the other hand, is the process by which cells break down glucose to release energy in the form of ATP. The three main stages of cellular respiration are glycolysis, the Krebs cycle, and oxidative phosphorylation.  

An apple tree does not require a specific amount of water "during a day" as it depends on various factors such as climate, soil moisture, and tree size. The answer "a bath full" is likely a humorous response indicating that the tree requires a significant amount of water, similar to filling a bath. However, it is important to note that the actual water requirement for an apple tree may vary and should be determined based on specific environmental conditions and the tree's needs.

In 1912, a link was made between smoking and cancer. This means that in this particular year, researchers or scientists discovered evidence or conducted studies that established a connection between smoking and the development of cancer.

Polar bears stay white all year round in order to be less visible to seals. The white fur helps them blend in with the snow and ice, making it easier for them to sneak up on their prey. Additionally, the white fur also helps to camouflage them from other predators. By staying white, polar bears are able to effectively hunt and survive in their Arctic environment.