Biology from the earliest cells to today’s mammals, reptiles, and birds. How cells evolved, the parts of a cell, the evolution of plants, and the relationships between plants and animals. Suitable for class worksheets or for informal homeschooling.

A first section on cells explains how cells evolved from small molecules found in space to amino acids, proteins, lipid membranes, RNA, and finally living cells. We trace the evolution of the parts of a cell. Chloroplasts come to live inside plant cells, while mitochondria come to live inside animal cells. We see how cells are still made up of the same simple building blocks – lipid membranes, RNA, and enzymes.

A second section traces the evolution of living creatures with more than one cell. Starting with sponges and hydras, we see how bilateral symmetry emerged, and how all complex creatures are basically shaped like worms: a hollow tube so food and oxygen can reach all our cells. We look at how worms evolved into eels and fish, lungfish, frogs, reptiles, birds, and mammals. There’s a section on primates and the evolution of modern humans.

A third section discusses the systems of human bodies and how they evolved. We trace the nervous system from single neurons to the development of the brain, including several articles on the evolution of eyes. There are similar sections for digestion, the circulatory system, and the respiratory system.

Finally, a fourth section suggests simple biology-related activities for classes or homeschoolers. These simple projects each reassure the student that science is based on observable facts. Compare the skeletons of chickens and fish. Try to grow plants under different conditions. Look at leaves changing color in the fall. Some activities require a microscope, but many require only things you have in the house already.

16 09, 2017

What are snakes? Evolution and biology

By |2019-07-16T08:16:34-07:00September 16th, 2017|Biology|0 Comments

Two pythons: evolution of snakes When did snakes evolve? Snakes evolved from lizards only about 150 million years ago, during the Jurassic Period. This is during the time of the dinosaurs, about the same time that the first birds evolved from small dinosaurs. What about lizards? More about dinosaurs Evolution of birds The Jurassic period All our biology [...]

6 09, 2017

Human organs: medieval science

By |2019-09-15T21:13:36-07:00September 6th, 2017|Biology, Science|0 Comments

Chinese drawing of the human organs (about 1200) Eyes and fevers Between the Middle Ages and modern times, doctors have learned a lot of new things about how human bodies work. Earlier history of the human body History of medicine History of science All our biology articles The Islamic doctor al-Tabari, in the early 800s, [...]

6 09, 2017

What is cholera? History of disease and medicine

By |2019-04-01T05:55:51-07:00September 6th, 2017|Biology, Science|0 Comments

History of cholera: Washing clothes in the river (India) Where did cholera get started? Cholera (KOLL-uh-rah) is a very serious sickness. It probably first got started in India. History of disease Indian doctors and medicine All our India articles When did cholera first make people sick? People in India were dying of cholera by [...]

28 07, 2017

Bilateral symmetry – Geometry

By |2019-02-14T07:17:30-07:00July 28th, 2017|Biology, Math|0 Comments

A butterfly has bilateral symmetry. Thanks to Wikimedia Commons What is bilateral symmetry? A shape has bilateral symmetry when it is the same on both sides of a line drawn down the middle. Are humans symmetrical? Venus of Lespugue, ca. 25000 BC, now in the Musee du Quai Branly, Paris You [...]

25 06, 2017

Silurian period – Fish get jaws

By |2018-04-19T11:29:11-07:00June 25th, 2017|Biology, Geology|0 Comments

Silurian period: Trout swimming When was the Silurian period? The beginning of the Silurian period was about 443 million years ago. Some environmental problem at the end of the Ordovician period (probably ice ages) killed most of the plants and animals on Earth. The creatures that survived this extinction were the ones that [...]

24 06, 2017

Quaternary period – modern times

By |2018-11-09T07:50:38-07:00June 24th, 2017|Biology, Geology|0 Comments

The Quaternary Period includes today - big cities and all When was the Quaternary Period? The Quaternary period began about 1.8 million years ago (1,800,000 years ago), coming after the Tertiary. The Quaternary is still going on today - we live in the Quaternary period. So far, it's a much shorter period than [...]

24 06, 2017

Proterozoic Eon – eukaryotes to worms

By |2018-04-21T11:56:39-07:00June 24th, 2017|Biology, Geology|0 Comments

Two and a half billion years ago, the Archaean Eon ended and the Proterozoic Eon began. Trillions of prokaryote cells lived in Earth's oceans. Some of these cells could photosynthesize their energy from sunlight, water, and carbon dioxide. These photosynthesizing cells pooped out a lot of oxygen. By about 2.3 billion years ago, the iron [...]

24 06, 2017

Devonian Period – fish, lungfish

By |2019-09-20T12:26:23-07:00June 24th, 2017|Biology, Geology|0 Comments

Coelocanth: a fish from the Devonian period When was the Devonian period? Four hundred and sixteen million years ago, when the Silurian period ended and the Devonian period began, most of the land on Earth was clumped together into a supercontinent called Gondwana. Silurian period Plate tectonics All our geology articles Life in [...]

3 06, 2017

Digestion – Oxidation reaction

By |2019-05-08T05:40:43-07:00June 3rd, 2017|Biology, Chemistry|2 Comments

Kids eating food (thanks to USDA) - get ready to digest food! How do you digest food? When animals, including people like you, digest their food, they use an oxidation reaction to break down big hydrocarbon molecules like sugar into different molecules. Cell digestion Digestive system What is an oxidation reaction? All our chemistry articles [...]

2 06, 2017

What is a protein? Organic chemistry

By |2017-06-02T23:46:07-07:00June 2nd, 2017|Biology, Chemistry|0 Comments

Proteins are a type of molecule made mainly out of hydrogen and carbon atoms. They are combinations of smaller molecules called amino acids. The first amino acids probably developed into proteins more than four billion years ago on Earth, possibly with the help of ribonucleic acid, or RNA. We don't know whether this process has happened on [...]