Biology Lessons & Help

Does the thought of learning more about yourself, the world, and all living things excite you? Do you want

to know what you’re made

of and how it functions? Then biology is the subject for you! Biology literally means “the study of life,” so

you’ll gain a much better understanding of how people, other animals, and plants live and support themselves. You can

also gain a better sense of why you have brown

hair or green eyes, or why some peas are green and others are yellow. Check out

our selection below to learn the basics of how nature exists! If you’re looking for personal assistance, check out our community of biology tutors.

Active Transport

Active transport occurs when a solute has to pass through the cell membrane against the concentration gradient.

This process requires energy to move the substance across the membrane. To find out more about how this process

works, read our lesson on active transport!

Animal and Plant Cells

This lesson describes the differences between animal and plant cells. For example, which type of cells has a cell

wall and plastids? If you don’t know, read the lesson to find out the answer and more information about animal and

plant cells!

Cell Cycle

Does anaphase come before or after telophase? Don’t know the answer? Read this lesson on the cell cycle to find

out more about what happens in each step of the cell cycle.

Cell Membrane

The cell membrane gives the cell structure and holds all organelles within the cell. It is made up of a

phospholipid bilayer, which is a scientific way of saying the membrane is made of phospholipids. Phosopholipids have

phosphate heads and lipid tails. To learn more about the nuances of the cell membrane, read this lesson!

Cell Structure and Function

The cell is the basic unit of life. All organisms are made up of cells, and cells come from other cells through

reproduction. Cells must also get nutrients and excrete waste. Read this lesson for more information on cells!

Cellular Respiration

There are two types of cell respiration: aerobic and anaerobic. Each begins with glycolysis but goes through a

different process after glycolysis is complete. For more information about how each type of respiration works, read

this lesson on cellular respiration!

Endocytosis and Exocytosis

The two types of bulk transport (that is, transport that allows proteins and polysaccharides in or out of the

cell) are endocytosis and exocytosis. In exocytosis, materials are pushed out of the cell via secretion. In

endocytosis, materials move into the cell. Read on for more specifics about endocytosis and exocytosis!


Evolution is the change in hereditary trains in a population over time. This lesson covers the mechanisms of

evolution as well as the results of evolution. After reading this lesson, test your understanding with a short quiz

on evolution!

Facilitated Diffusion

Facilitated diffusion is a method of passive transport that specifically serves large molecules, like glucose.

It’s performed by various proteins embedded in the cell membrane. For more specifics on facilitated diffusion, read

this lesson!

Genetics Overview

Genetics is the study of genes, which are units that encode genetic characteristics. The genetic code is encoded

on chromosomes, which are passed from generation to generation. Read more about genetics to find out how we inherit

our traits!


Glycolysis is the first step in the process of ATP synthesis. It is the anaerobic breakdown of glucose into

pyruvate. There are ten steps to glycolysis – read this lesson to learn what each of the steps does!


One of the best examples of an organism maintaining homeostasis is the human body – internal systems, like body

temperature, are maintained regardless of outside conditions. This lesson goes over terms like the receptor, control

center, and effector, all of which contribute to maintaining a homeostatic state. Read this lesson for more

information on homeostasis!

Krebs Cycle

The Krebs Cycle is also known as the Citric Acid cycle or the TCA (tricarboxylic acid) cycle. This cycle regulates

the oxidation of glucose, thereby demonstrating the role biochemistry plays in the study of biology. Read this lesson

for more information on the Krebs Cycle!

Meiosis and Mitosis

Meiosis and mitosis are both forms of cellular division; however, mitosis results in diploid, eukaryotic cells

whereas meiosis results in haploid cells, or gametes. Gametes are needed for sexual reproduction, whereas diploid

cells are necessary for the growth of the organism. Read this lesson for more on the similarities and differences of

meiosis and mitosis.

Mendel’s Laws

While it was generally understood in the 1800s that children inherited traits from their parents, Mendel’s

experiments shed light on how the inheritance occurs in different species. Read this lesson for more about how

Mendel’s experiments contribute to our present-day understanding of genetics.


The main idea behind metabolism is the process of ingesting food (nutrients) which are broken down and digested by

the body to produce energy. Metabolism is seen in two phases: catabolism and anabolism. Catabolism breaks down fats,

proteins, and carbs; then anabolism uses the energy to build components of a cell. Read this lesson to find out more

about the intricacies of metabolism!

Natural Selection

Natural selection is a mechanism of evolution. The concept was brought into the public sphere by Charles Darwin in

1859. Read this lesson for more on the history of natural selection.

Passive Transport

Related to active transport, passive transport is a type of transport processes that do not require energy from a cell. Processes such as diffusion, osmosis, and facilitated diffusion are all examples of passive transport. Read this lesson for a detailed explanation and a helpful practice quiz.


The process of plants creating and storing sugar molecules to produce energy is called photosynthesis.

Photosynthesis takes light and converts it to chemical energy, which plants can store. Photosynthesis consists of

light-dependent and light-independent reactions. Read on to find out more information about photosynthesis!

Prokaryotes and Eukaryotes

This lesson details the differences between prokaryotes and eukaryotes. It also has a fantastic image that

displays similar organelles and cell-specific organelles! Read this lesson for more information on prokaryotes and


Properties of Water

Found throughout nature, water is a necessary component of most organic reactions. It’s the most common compound

on the surface of our planet! Read this lesson to find out specific details of the properties of H2O.

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