7th Grade Life Science

A giraffe is an herbivore because it primarily feeds on leaves, shoots, and fruits from trees. Its long neck and tongue allow it to reach high branches, where it can find its main source of food. Unlike the other options, the giraffe does not eat meat or insects, making it the only herbivorous animal listed.

The nucleus is considered the "brain" of a cell because it contains the cell's genetic material, including DNA, which directs the cell's activities and controls its functions. The nucleus also regulates the synthesis of proteins through the production of RNA, which is then transported to the ribosomes for protein synthesis. Additionally, the nucleus plays a role in cell division and replication, making it a crucial component in the overall functioning of a cell.

The bicep and tricep muscles are located in the upper arm and work together as a pair to move the arm. The bicep muscle is responsible for flexing the arm at the elbow joint, while the tricep muscle is responsible for extending the arm. These muscles have an antagonistic relationship, meaning that when one contracts, the other relaxes. This allows for smooth and coordinated movement of the arm.

Athlete's foot is a common fungal infection that affects the skin on the feet. It is caused by a group of fungi called dermatophytes. These fungi thrive in warm and moist environments, such as locker rooms and swimming pool areas. They can be easily transmitted through direct contact with infected surfaces or by sharing personal items like towels or shoes. The fungi feed on the dead skin cells and multiply, leading to symptoms like itching, redness, and cracking of the skin. Therefore, the correct answer is fungus.

A producer is an organism that makes its own food through a process called photosynthesis. This process involves using sunlight, carbon dioxide, and water to produce glucose and oxygen. Producers, such as plants and some types of bacteria, are able to convert these raw materials into energy-rich molecules that they can use for growth and survival. This ability to produce their own food sets producers apart from other organisms that rely on consuming other organisms for energy.

Nicotine is the addictive chemical in cigarettes. It is a highly addictive substance that stimulates the release of dopamine in the brain, creating a pleasurable sensation and reinforcing the desire to continue smoking. Nicotine addiction can lead to physical and psychological dependence, making it difficult for individuals to quit smoking. Tar and carbon dioxide are harmful components of cigarette smoke, but they are not the addictive chemicals.

Testosterone is the hormone that controls changes in boys at puberty. During puberty, the production of testosterone increases, leading to the development of secondary sexual characteristics such as deepening of the voice, growth of facial and body hair, enlargement of the testes, and muscle development. Estrogen is the primary female sex hormone, and while it also plays a role in male development, testosterone is the main hormone responsible for the changes that occur during puberty in boys. The amygdala is a part of the brain involved in emotion and memory processing, but it is not a hormone.

Red blood cells carry oxygen in the body. They contain a protein called hemoglobin, which binds to oxygen in the lungs and transports it to the body's tissues. This process is essential for delivering oxygen to all cells and organs, ensuring their proper functioning. White blood cells, platelets, and fibrin cells have different functions in the body, such as fighting infections, clotting blood, and repairing damaged tissues, but they do not carry oxygen like red blood cells do.

UV rays are the most damaging sun rays because they have a higher energy level than visible light or infrared rays. UV rays can penetrate the skin and cause damage to the DNA in skin cells, leading to sunburn, premature aging, and an increased risk of skin cancer. It is important to protect the skin from UV rays by using sunscreen, wearing protective clothing, and seeking shade during peak sun hours.

The correct answer is cell wall and chloroplasts. Plant cells have a rigid cell wall made of cellulose, which provides structural support and protection. Animal cells do not have a cell wall. Additionally, plant cells contain chloroplasts, which are responsible for photosynthesis and contain chlorophyll. Animal cells do not have chloroplasts. This distinction in cell wall and chloroplasts is what sets plant cells apart from animal cells.

Green plants take in carbon dioxide (CO2) during photosynthesis and produce oxygen (O2) as a byproduct. This process is essential for the survival of many organisms on Earth as it helps to maintain the balance of gases in the atmosphere.

The femur, vertebra, and ribs are the correct answer because these bones play a crucial role in supporting the body. The femur, the longest and strongest bone in the body, supports the weight of the upper body and allows for movement. The vertebrae form the spinal column, providing support and protection for the spinal cord while allowing for flexibility. The ribs protect the vital organs in the chest and also contribute to the stability of the upper body.

AIDS and HPV (warts) are two STDs that cannot be cured. AIDS is caused by the Human Immunodeficiency Virus (HIV) and attacks the immune system, making it difficult for the body to fight off infections and diseases. While there are antiretroviral drugs that can help manage HIV, there is currently no cure. HPV is a viral infection that can cause genital warts and certain types of cancer. While the warts can be treated and removed, there is no cure for the underlying HPV infection.

The correct food chain is sunflower - mouse - hawk. In a food chain, energy flows from one organism to another through the consumption of food. In this case, the sunflower is a producer that converts sunlight into energy through photosynthesis. The mouse then consumes the sunflower for energy, and finally, the hawk preys on the mouse for its energy needs. This sequence follows the natural flow of energy in an ecosystem.

Constipation occurs when food moves too slowly through the intestines. This can happen due to various reasons such as lack of fiber in the diet, inadequate fluid intake, lack of physical activity, certain medications, or medical conditions like irritable bowel syndrome or hypothyroidism. When food moves slowly through the intestines, more water is absorbed from it, resulting in dry and hard stools that are difficult to pass. Increasing fiber intake, staying hydrated, exercising regularly, and addressing any underlying medical conditions can help alleviate constipation.

The mandible is a bone that is commonly known as the jawbone. It is the largest and strongest bone in the human face and forms the lower jaw. It is connected to the skull by the temporomandibular joint, allowing for movements such as chewing and speaking. Therefore, the correct answer is "in the jaw."

Bacteria can be seen best at 400X power on our microscopes because at this magnification, the bacteria are enlarged enough to be visible and their details can be observed clearly. Lower powers such as 50X may not provide enough magnification to clearly see the bacteria, while higher powers such as 100X may result in a blurry image or may not be suitable for observing bacteria.

Identical twins form when one egg is fertilized and splits. This occurs when a single fertilized egg, also known as a zygote, divides into two separate embryos. As a result, both embryos have the same genetic information and develop into identical twins. This is different from fraternal twins, which form when two separate eggs are fertilized by two different sperm.

Cartilage serves the function of both protecting the ends of bones and making bones move more easily. It acts as a cushion between bones, preventing them from rubbing against each other and causing damage. Additionally, cartilage reduces friction and allows for smooth movement at joints, enabling bones to glide and articulate with ease. Therefore, the correct answer is both.

Food stays in the stomach for about 6 hours. After we eat, the food enters the stomach where it is broken down by stomach acids and enzymes. This process takes approximately 2-4 hours. Once the food is broken down into a liquid-like substance called chyme, it gradually moves into the small intestine for further digestion and absorption of nutrients. Therefore, the correct answer is 6 hours.

The small intestine is the correct answer because it is the primary site where the absorption of nutrients from digested food occurs. It is lined with specialized cells called villi, which increase its surface area for efficient absorption. The small intestine receives partially digested food from the stomach and further breaks it down using digestive enzymes. Nutrients such as carbohydrates, proteins, fats, vitamins, and minerals are absorbed into the bloodstream through the walls of the small intestine and then transported to the body's cells for energy and other functions.

Capillaries are the small vessels that connect arteries and veins. They are responsible for the exchange of oxygen, nutrients, and waste products between the blood and the surrounding tissues. Capillaries have thin walls and a large surface area, which allows for efficient diffusion of substances. Arterioles are small branches of arteries, valves are structures that prevent backflow of blood, and vessels is a general term that includes arteries, veins, and capillaries. Therefore, the correct answer is capillaries.

Based on the given information, it can be inferred that the air quality has been consistently within the range of 30-40.

The large artery that carries blood to the brain and body is called the aorta. The aorta is the main artery that originates from the left ventricle of the heart and distributes oxygenated blood to all parts of the body through its branches. It is responsible for supplying vital oxygen and nutrients to the brain and other organs, making it a crucial component of the circulatory system.

The windpipe, also known as the trachea, is responsible for carrying air from the nose and mouth to the lungs. It is a tube-like structure that is located in the neck and chest area. The trachea is made up of rings of cartilage to keep it open and prevent collapse. It is an important part of the respiratory system and plays a crucial role in breathing. The esophagus, on the other hand, is responsible for carrying food from the mouth to the stomach, while the sphincter is a circular muscle that controls the flow of substances in the body. The epiglottis is a flap of tissue that prevents food from entering the windpipe during swallowing.

If you have 20/40 vision, it means that you can see at 20 feet what most people with normal vision can see at 40 feet. This indicates that your visual acuity is below average, as you need to be closer to an object to see it clearly compared to someone with 20/20 vision.

The normal human heart rate is about 60 beats per minute. This is considered the average resting heart rate for adults. During physical activity or stress, the heart rate may increase, but at rest, a rate of 60 beats per minute is considered normal.

A screaming child produces about 80 decibels of sound. Decibels are a unit used to measure the intensity of sound. 80 decibels is considered quite loud, similar to the sound of a busy street or a vacuum cleaner. This level of noise can be disruptive and may cause discomfort to those nearby.

This statement is always true because an erection is the result of increased blood flow to the penis, causing it to become firm and erect. Ejaculation, on the other hand, is the release of semen from the penis. In the normal sequence of events during sexual arousal, an erection occurs first, followed by ejaculation. Therefore, it can be said that erections always come before ejaculations.

Chickens have fused phalanges means that the bones in their wings are joined together, unlike human arms where the phalanges are separate. This structural difference allows chickens to have a more rigid wing structure, which is necessary for flight.

Blood type O is considered recessive because it does not have any antigens on the surface of red blood cells. This means that it can be donated to individuals with any blood type, making it the universal donor. In contrast, blood types A, B, and AB all have antigens on their red blood cells, making them dominant over type O.

The majority of the Earth's atmosphere is composed of nitrogen. It makes up about 78% of the air we breathe. Oxygen, carbon monoxide, carbon dioxide, and other gases make up the remaining percentage. Nitrogen is essential for life as it is a key component of proteins and nucleic acids. It is also used in various industrial processes and plays a crucial role in maintaining the Earth's climate and weather patterns.

The diaphragm on a microscope controls the amount of light that passes through the specimen. By adjusting the diaphragm, the user can increase or decrease the amount of light reaching the specimen, which can help in achieving optimal visibility and clarity during observation.

Veins carry blood that is low in oxygen. Unlike arteries, which carry oxygen-rich blood away from the heart to the rest of the body, veins transport oxygen-depleted blood back to the heart. This blood has delivered oxygen to the body's tissues and organs and is now returning to the heart and lungs to be replenished with fresh oxygen.

The cerebrum is the part of the brain that controls the five senses. It is the largest part of the brain and is responsible for processing sensory information, such as sight, hearing, taste, smell, and touch. It plays a crucial role in interpreting and making sense of the world around us. The cerebrum is divided into two hemispheres and is responsible for higher cognitive functions, including memory, language, and problem-solving.

The deltoid muscle is not an example of a smooth muscle because it is a skeletal muscle. Smooth muscles are found in the walls of organs and blood vessels, and they are involuntary muscles. The diaphragm, iris, and intestine are all examples of smooth muscles because they are found in organs and have involuntary control.

The cervix is the correct answer because it is the muscle that holds the baby in the uterus during pregnancy. It acts as a barrier between the uterus and the vagina, preventing the baby from descending prematurely. The cervix also undergoes changes during labor, dilating and thinning to allow the baby to pass through during childbirth.

The dermis is the layer of skin that contains blood vessels, which is why it bleeds when you cut it. The epidermis is the outermost layer of the skin, and the fat layer is located beneath the dermis. However, neither of these layers contain blood vessels, so they would not bleed when cut.

The nosepiece is the correct answer because it is the part of the microscope that holds the lenses and rotates. It allows the user to switch between different objective lenses, which are essential for adjusting the magnification of the microscope. The nosepiece is typically located near the bottom of the microscope's body tube and is easily accessible for rotating and changing lenses.

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On agar, bacteria appear flat and colorful. Agar is a gelatinous substance used as a growth medium in laboratories to culture bacteria. When bacteria grow on agar, they form colonies that are typically flat and can exhibit a range of colors depending on the type of bacteria and the nutrients present in the agar. This characteristic appearance helps in identifying and distinguishing different bacterial species.

The left side of the heart is the correct answer because it is responsible for pumping oxygenated blood to the rest of the body. The left ventricle, which is part of the left side of the heart, is the most muscular chamber in the heart. It has thicker walls compared to the right ventricle because it needs to generate enough force to pump blood throughout the body's systemic circulation.

The semicircular canals are the part of the ear that controls balance, not hearing. These canals are filled with fluid and contain sensory hair cells that detect changes in head position and movement. When the head moves, the fluid in the canals also moves, causing the hair cells to send signals to the brain, which helps maintain balance and coordination. The cochlea is responsible for hearing, the eustachian tube helps equalize pressure in the middle ear, and the eardrum helps transmit sound vibrations.

The most common blood type among Americans is O. This is because blood type O is the most widely distributed blood type in the general population. Approximately 45% of Americans have blood type O, making it the most prevalent blood type in the country.

A karyotype is a picture of chromosomes that have been cut apart and arranged in order of size. It is used to study the number, size, and shape of chromosomes in an individual's cells. By examining a karyotype, genetic abnormalities or disorders can be identified. Therefore, a karyotype is the correct term to describe a picture of chromosomes that is cut apart and arranged in order of size.

The genotype "tt" does not allow tasting in PTC tasting ability. This is because the "t" allele is a non-functional allele that results in the inability to taste the chemical PTC. The other genotypes, "TT" and "Tt", have at least one functional allele and therefore allow tasting.

Omnivores are at the top of food chains because they have a diverse diet, consuming both plants and animals. This allows them to obtain energy from multiple sources and gives them an advantage in terms of survival and adaptation. Omnivores have the ability to feed on both herbivores and carnivores, making them higher up in the food chain compared to other animals.

The tapetum is the eye part that allows animals to see in low light. It is a reflective layer located behind the retina in the back of the eye. This layer helps to enhance night vision by reflecting light back through the retina, giving it a second chance to be detected by the photoreceptor cells. This is why animals with a tapetum, such as cats and dogs, have better night vision than humans. The retina, iris, and sclera are other parts of the eye, but they do not specifically contribute to low light vision.