What I've Learned in Biology

From DNA to Spaceship Earth

What is life

Life is a characteristic that separates animate and inanimate objects
For something to be living it must grow, react to stimuli, reproduce, and undergo metabolism
The only known life is on Earth and began over 3.5 billion years ago

How does life work

All life goes through reproduction and creates offspring
When an organism produces offspring it passes on its genes the offspring
Genes are the traits that define every organism that makes them unique
Genes are contained in DNA which is contained in chromosomes

What is DNA

DNA is a molecule found in all living organisms
It stores genes in a combination of adenine, cytosine, guanine, and thymine
It is in the shape of a double helix with bars connecting each side
DNA goes through replication when a cell divides

Why are there so many diferent kinds of life

All life on Earth came from a single common ancestor approximately 3.5 billion years ago
That first cell evolved over many generations into all the life there is and ever has been
Evolution is a change in a species characteristics over many generations
Over time different species evolved to be better suited for different environments creating many new species

Classification of life

There are 3 domains of life: archaea, bacteria, eukarya
Life is classified into several increasingly more specific categories - kingdom, phylum, class, order, family, genus, species

How lifeforms interact with eachother

How life interacts with Earth

All life on Earth is dependent on each other in one way or another
Just like how different species are classified different conditions for life are also classified
The most specific category is a niche
Each niche is has slightly diferent conditions from any other
Only one species can inhabit each niche