Life Science
Life science questions will assess your knowledge/understanding of:
- Living things and their environments
- Competition and interaction among living things
- The relationship and functions of living systems
- Human body systems
That said, let’s review some life sciences basics. Remember, becoming familiar with these terms and ideas is your goal, not memorization.
Cells
Cells are the building blocks of life. Each contains a cell wall (plants) or cell membrane (animals) that separates it from other cells. Inside are different structures known as organelles. Each organelle has a specific function. Here are a few you need to know:
- Nucleus: Contains the genetic information in the form of DNA.
- Mitochondrion: Generates chemical energy the cell needs to live.
- Vacuole: Contains water and maintains the cell’s pH. More important in plant cells’ functions than animal cells’ functions.
- Lysosome: Helps the cell break down chemicals. Acts as a type of waste-disposal system for the cell.
Cells divide through a complex process known as mitosis. Although you need not memorize the steps, it’s good to know the stages and approximately what each one does:
- Prophase: The nucleus begins to change, signaling the beginning of cell division.
- Prometaphase: The small membrane around the nucleus dissolves.
- Metaphase: Chromosomes line up for separation.
- Anaphase: Chromosomes pull apart from one another and move to opposite sides of the cell.
- Telophase: Two membranes form around each set of identical genetic information, and the cell splits in two.
Animals
There are two broad categories of animals: invertebrates and vertebrates. Invertebrates, such as insects, corals, and crabs, do not have a spinal column. Vertebrates, such as amphibians, fish, birds, and mammals, do have a spinal column.
Here are some 100% need-to-know facts about major categories of animals.
Mammals
Mammals are warm-blooded (i.e., they can regulate their body temperature) and give birth to live young.
Birds
Birds, the descendants of dinosaurs, lay eggs and have feathers. Not all can fly.
Amphibians
Amphibians are cold-blooded (i.e., they cannot regulate their body temperature) and lay eggs.
Fish
Fish use gills to extract oxygen from water and lay eggs. Some fish can live only in salt water, while others can live only in freshwater.
Worms
An invertebrate with no eyes or limbs. Different species live in different environments, and some are parasitic.
Mollusks
A diverse collection of species known for their soft but muscular bodies and unique nervous systems.
Arthropods
A group of about ten-million invertebrate species that include insects and shrimp. All arthropods have an exoskeleton, meaning their skeleton exists on the outside, rather than the inside. Humans, birds, and other animals have an endoskeleton, meaning their skeleton exists on the inside.
Behaviors
Living things perform different behaviors. These behaviors fall into one of four categories:
- Instinct: A behavior that does not require thinking or learning. In the winter, a bear’s instinct tells it to hibernate.
- Learned Behavior: A behavior that requires learning. Young lion cubs learn to hunt by watching their parents.
- Reflex: A reflex is a behavior rooted in a biological structure or process. Your hand immediately pulls away from a hot surface to prevent burns due to feedback mechanism in your body.
- Self-Preservation: A type of instinct, self-preservation is behaviors that increase a living thing’s chances of survival. An animal may keep itself hidden if it senses that predators are nearby.
Plants
Plants are a branch of life that use sunlight, water, carbon dioxide in the air, and minerals in the soil to produce oxygen. They use roots to extract water/minerals, such as nitrogen. In leaves and other structures, they perform photosynthesis, a complex chemical reaction that turns sunlight into energy. Leaves are green because this color makes photosynthesis the most efficient. The green color comes from a pigment called chlorophyll.
Many plant species share common structures, such as a central stem. They produce pollen to reproduce. Bees and other insects pollinate plants while collecting their nectar from flowers. The pollen attaches itself to insects and then is deposited onto other plants.
Although fungi are a separate branch of life, they share some similarities with plants. They have similar cell structures and growth patterns. However, fungi reproduce asexually from spores rather than seeds. Many fungi rely on the wind to carry their spores to new areas.
Heredity
Heredity is the process by which living things pass down their traits (e.g., hair and eye color) to the next generation. Nineteenth-century monk Gregor Mendel was the first scientist to discover how heredity works. He bred pea plants and discovered which traits were dominant and recessive. A dominant trait from one parent will always appear in the next generation, while a recessive trait will not appear unless both parents have the recessive trait.
Although Mendel discovered heredity, he could not explain how it happened. The discovery of DNA and RNA in the 20th century revealed the process of how living things passed down their traits. The discovery led to the birth of genetics, a field of biology focusing on how living things express and pass down genes – the biological foundation of traits.
The field of genetics has led to many breakthroughs, such as uncovering genetic disorders, disorders passed from parents to children. Today, aspiring parents can have their DNA tested to see which disorders they may pass on to their children. Other genetic disorders happen because of a mutation. A mutation is when a mistake takes place during mitosis. Mutations can lead to diseases such as cancer.
Human Anatomy
Doctors need at least four years of medical school to memorize human anatomy, but you only need four minutes to review the information necessary to excel on HiSET test day.
Nervous System: The nervous system sends electrical signals from different parts of the body to the brain. This network lets the body react to dangerous situations, such as pulling away from a hot surface or producing ‘fight or flight’ hormones.
Respiratory System: Every time you breathe, your respiratory system (e.g., the lungs) absorbs oxygen and expels carbon dioxide.
Digestive System: Consisting of the stomach and intestines, the digestive system breaks down food, absorbs vital nutrients, and expels solid waste.
Circulatory System: Your heart, arteries, and veins pump oxygenated blood from the lungs into every part of your body. Your body’s metabolism creates carbon dioxide, which your circulatory system brings back to the lungs so you can exhale it.
Skeletal System: Your skeletal system supports and protects your body’s organs, muscles, and other tissues. The skeletal system’s other functions include producing new blood cells.
The majority of the human body consists of three common elements:
Oxygen, Carbon, and Hydrogen
Health
Staying healthy is a challenge for a lot of people, especially those who have a heredity disease. Heredity diseases, such as sickle cell anemia or Huntington’s, are passed down through the genes. People can also develop an environmental disease, such as cancer caused by exposure to lead, asbestos, or carbon monoxide.
People with immunodeficiency have the hardest challenge staying healthy, as their bodies aren’t great at fending off infection and disease. Fortunately, these and other people can attain acquired immunity from certain diseases through vaccination. Vaccination creates a mild immune response that trains your body to fight off common illness such as the flu and COVID-19.
Although a doctor may treat your disease if you get really sick, it’s the job of public health professionals to study trends in illness and educate people about health best practices.