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Classification of Life

Scientists estimate that there are between 3 million and 100 million species of organisms on Earth.

___________________________________________--biologists who specialize in identifying and classifying life on our planet--have named approximately 1.7 million species so far.

Each year, about 13,000 _______________ ______________________are added to the list of known organisms.

So, how do scientists ____________________________ (organize) all these millions of species?

Two Types of Cells

Prokaryote:

Eukaryote:

List similarities and differences between Prokaryotes and Eukaryotes.

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The History of Life on Earth

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Multicellular eukaryotes (with nuclear membrane) evolved about 1 billion years ago.

For 2.6 billion years, life was unicellular.

Life began on Earth 3.6 billion years ago as a prokaryotic cell (single-celled organism with no nuclear membrane).

The Earth formed 4.5 billion years ago.

Line length reflects evolutionary distance. Note the close spacing of the groups plants (maize), fungi (yeast) and animals (humans)We’ve got a lot more in common with bacteria and plants than we think!

Animals diversified in the ocean about 600 million years ago. Plants colonized land about 440 million years ago and were followed shortly by animals. Humans of any sort are a very recent evolutionary development (~ 7 million years ago)

Archaea: The Archaea are one of two groups of prokaryotic organisms, organisms with

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no nuclear membrane. (Bacteria are the other group.)

Archaea are believed to be the earliest form of life on Earth. Although both archaea and bacteria are simple life-forms, archaea are very different from bacteria.

Archaea do not require sunlight for photosynthesis, as plants do, and they do not need oxygen. Archaea absorb CO2, N2, or H2S and give off methane gas as a waste product.

Archaea are best known for living in extremely hostile environments

Bacteria:

The Most Abundant Organisms There are more bacteria in your mouth

than there have been people living since the dawn of humans.

Bacteria are the primary recyclers of materials in the environment, particularly nitrogen.

Bacteria are also essential for many processes we depend on – sewage treatment, cheese production, antibiotic production, and biotechnological processes like gene cloning and protein production.

Bacteria are used to produce insulin and other drugs that people need.

The Domain ______________________________is divided into _____ _________________________________.

Protists

Protists are eukaryotes because they all have a nucleus. o Most have mitochondria. o Many have chloroplasts with which they carry on photosynthesis. o Many are unicellular and all groups (with one exception) contain some unicellular

members. A better name for Protists would be "Eukaryotes that are neither Animals, Fungi, nor Plants".

Fungi Fungi sometimes look like plants, but they’re not! Fungi can’t do photosynthesis, because they don’t have chloroplasts; they get their nutrients

from the organic material they live in. Decomposers, like mushrooms, feed on dead organic material. Some fungi feed on living organisms, such as plants, animals and even other fungi. This

causes diseases and infections in these organisms (like athlete’s foot and ringworm in humans).

Some fungi live as symbiotic partners with algae. The result: lichen (pronounced “like-n”).

Name_________________________________________ Date___________Living Environment Period_________Other differences from plants:

fungi don’t have roots, they have a mycelium. fungi’s cell walls are made of chitin, not cellulose

____________________________________ or classification, enables scientists to assign a very specific name to every species, so that scientists all over the world know exactly what species is being referred to.

Dichotomous KeyTool used by biologists to identify an unknown organismSeries of paired statements of anatomical description that leads to an ________________________.

Bird W:

Bird X:

Bird Y:

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Bird Z:

Using the dichotomous key, which organism is in the picture below? ___________________________________________.

1. a) animal has a spine…………………..go to 2 b) animal has no spine………..…invertebrate

2. a) animal has no gills and fins……..…. go to 3 b) animal has gills and fins…………….. Fish

3. a) animal has no scales…………..........go to 4 b) animal has scales………………..….reptile4. a) animal has feathers …………………..bird b) animal has no feathers ……………..go to 55. a) animal has hair…………………….mammal b) animal has no hair………………..amphibian