Biological evolution is the process of descent with modification over generations that produces the diversity of life on Earth. Evolution occurs through genetic inheritance over generations and is driven by natural selection. Over millions of years, this process of descent with modification resulted in the tremendous diversity of life we see today, as all organisms share a common ancestor. Evolution helps explain the history and relationships between different forms of life.

3.  An introduction to evolution
 Leaves on trees change color and fall over several weeks. Mountain
ranges erode over millions of years. A genealogy illustrates change with
inheritance over a small number of years. Over a large number of years,
evolution produces tremendous diversity in forms of life.
The definition Biological evolution, simply put, is descent with
modification. This definition encompasses small-scale evolution (changes in
gene frequency in a population from one generation to the next) and large-scale
evolution (the descent of different species from a common ancestor over many
generations). Evolution helps us to understand the history of life.
The explanationn Biological evolution is not simply a matter of change
over time. Lots of things change over time: trees lose their leaves, mountain
ranges rise and erode, but they aren't examples of biological evolution because
they don't involve descent through genetic inheritance.
 The central idea of biological evolution is that all life on Earth shares a common
ancestor, just as you and your cousins share a common grandmother.
 Through the process of descent with modification, the common ancestor of life
on Earth gave rise to the fantastic diversity that we see documented in the fossil
record and around us today. Evolution means that we're all distant cousins:
humans and oak trees, hummingbirds and whales.

4. Mountain ranges erode over millions of years.
Leaves on trees change color and fall over
several weeks.
A genealogy illustrates change with Over a large number of years, evolution
inheritance over a small number of years. produces tremendous diversity in forms of
life.

5. The history of life: looking at the patterns
The central ideas of evolution are that life has a history — it has changed over time — and that
different species share common ancestors.
Here, you can explore how evolutionary change and evolutionary relationships are represented in
"family trees," how these trees are constructed, and how this knowledge affects biological
classification. You will also find a timeline of evolutionary history and information on some specific
events in the history of life: human evolution and the origin of life.

6. The family tree
The process of evolution produces a pattern of
relationships between species. As lineages evolve
and split and modifications are inherited, their
evolutionary paths diverge. This produces a
branching pattern of evolutionary relationships.
By studying inherited species' characteristics and other
historical evidence, we can reconstruct evolutionary
relationships and represent them on a "family tree,"
called a phylogeny. The phylogeny you see below
represents the basic relationships that tie all life on
Earth together.
The three domains
This tree, like all phylogenetic trees, is a hypothesis about the relationships among organisms. It illustrates the
idea that all of life is related and can be divided into three major clades, often referred to as the three domains:
Archaea, Bacteria, and Eukaryota. We can zoom in on particular branches of the tree to explore the phylogeny
of particular lineages, such as Animalia (outlined in red). And then we can zoom in even further to examine
some of the major lineages within Vertebrata. Just click the button below.
The tree is supported by many lines of evidence, but it is probably not flawless. Scientists constantly reevaluate
hypotheses and compare them to new evidence. As scientists gather even more data, they may revise these
particular hypotheses, rearranging some of the branches on the tree. For example, evidence discovered in the
last 50 years suggests that birds are dinosaurs, which required adjustment to several "vertebrate twigs."

7. Important events in the history of life
A timeline can provide additional information about life's history not visible on an evolutionary tree. These
include major geologic events, climate changes, radiations of organisms into new habitats, changes in
ecosystems, changes in continental positions, and widespread extinctions. Explore the timeline below to
review some of the important events in life‘ s
history.

8. Microbiology (
from Greek mīkros, "small"; bios, "life"; and --logia) is the study of microscopic
organisms, which are defined as any living organism that is either a single cell
(unicellular), a cell cluster, or has no cells at all (acellular).This includes eukaryotes,
such as fungi and protists, and prokaryotes. Viruses and prions, though not strictly
classed as living organisms, are also studied. Microbiology typically includes the
study of the immune system, or immunology.
Microbiology is a broad term which includes virology, mycology, parasitology,
bacteriology, immunology and other branches. A microbiologist is a specialist in
microbiology and these

9. Bacteria

10. Bacteria are of such immense importance because of their extreme flexibility,
capacity for rapid growth and reproduction, and great age - the oldest fossils known,
nearly 3.5 billion years old, are fossils of bacteria-like organisms.
• One feature that has enabled them to spread so far, and last so long is their ability
to go dormant for an extended period.
• Bacteria were first observed by Antonie van Leeuwenhoek in 1676, using a single-
lens microscope of his own design. He called them "animalcules" The name
Bacterium was introduced much later, by Christian Gottfried Ehrenberg in
1828.In fact, was a genus that contained non-spore-forming rod-shaped bacteria,
as opposed to Bacillus, a genus of spore-forming rod-shaped bacteria defined by
Ehrenberg in 1835.
• In 1910, Paul Ehrlich developed the first antibiotic,
• A major step forward in the study of bacteria was the recognition in 1977 by Carl
Woese that archaea have a separate line of evolutionary descent from bacteria

11. Endospores
Certain genera of Gram-positive bacteria,can form highly resistant, dormant
structure.

12. • Properties of Bacteria
• prokaryotic (no membrane-enclosed nucleus)
• no mitochondria or chloroplasts
• a single chromosome
• a closed circle of double-stranded DNA
• have a rigid cell wall made of peptidoglycan. Link to illustrated discussion of the
structure.
• reaction to the Gram stain.
Classification of Bacteria
• Until recently classification has done on the basis of such traits as: shape
• bacilli: rod-shaped
• cocci: spherical
• spirilla: curved walls
• The bacterial cells are first stained with a purple dye called crystal violet.
• Then the preparation is treated with alcohol or acetone.
• This washes the stain out of Gram-negative cells.
• Bacteria that are not decolorized by the alcohol/acetone wash are Gram-positive.

13. • Aerobic bacteria thrive in the presence of oxygen and require it for their continued
growth and existence.
• Other bacteria are anaerobic, and cannot tolerate gaseous oxygen, such as those
bacteria which live in deep underwater sediments, or those which cause bacterial
food poisoning.
• The third group are the facultative anaerobes, which prefer growing in the
presence of oxygen, but can continue to grow without it.
• Bacteria grow to a fixed size and then reproduce through binary fission, a form of
asexual reproductionnder optimal conditions, bacteria can grow and divide
extremely rapidly, and bacterial populations can double as quickly as every 9.8
minutes.
• Bacterial growth follows three phases. The first phase of growth is the lag phase, a
period of slow growth when the cells are adapting to the high-nutrient environment
and preparing for fast growthThe second phase of growth is the logarithmic phase
(log phase), also known as the exponential phase. The log phase is marked by
rapid exponential growth.The final phase of growth is the stationary phase and is
caused by depleted nutrients. The cells reduce their metabolic activity and consume
non-essential cellular proteins.

14. Bacteriophages are viruses that infect bacteria.
Pathogens
• If bacteria form a parasitic association with other organisms, they are classed as
pathogens. Pathogenic bacteria are a major cause of human death and disease and
cause infections such as tetanus, typhoid fever, diphtheria, syphilis, cholera,
foodborne illness, leprosy and tuberculosis.
• Bacterial diseases are also important in agriculture, with bacteria causing leaf spot,
fire blight and wilts in plants, as well as Johne's disease, mastitis, salmonella and
anthrax in farm animals.
• Bacterial infections may be treated with antibiotics, which are classified as
bacteriocidal if they kill bacteria, or bacteriostatic if they just prevent bacterial
growth.
Significance in technology and industry
acteria, often lactic acid bacteria such as Lactobacillus and Lactococcus, in
combination with yeasts and molds, have been used for thousands of years in the
preparation of fermented foods such as cheese, pickles,vinegar, wine and yogurt.

15. Virus

16. Archea

17. • are a group of single-celled microorganisms.
• A single individual or species from this domain is called an archaeon
(sometimes spelled "archeon").
• Archaea were first classified as a separate group of prokaryotes in 1977 by
Carl Woese and George E. Fox.
• The search for fossils of Archaea faces a number of problems. First of all,
they're very tiny organisms and so will leave microscopic fossils.
• Archaea and Bacteria cells may be of similar sizes and shapes,Instead of
physical features, micropaleontologists rely on chemical features.
chemical traces have even been found in sediments from the Isua district
of west Greenland, the oldest known sediments on Earth at about 3.8
billion years old.

18. Fungi

19.  The English word fungus is directly adopted from the Latin
fungus (mushroom)The use of the word mycology, which is
derived from the Greek mushroom)to denote the scientific study
of fungi.
 a recent (2011) estimate suggests there may be over 5 million
species.
 The living body of the fungus is a mycelium made out of a web of
tiny filaments called hyphae, which are cylindrical, thread-like
structures 2–10 µm in diameter and up to several centimeters in
length.
 Fungi feed by absorbing nutrients from the organic material in
which they live.
 You probably use fungal products every day without being aware
of it. Other fungi provide numerous drugs (such as penicillin
and other antibiotics), foods like mushrooms. Fungi also cause a
number of plant and animal diseases: in humans, ringworm,
athlete's foot, and several more serious diseases are caused by
fungi.

20.  Another feature of fungi is the presence of chitin in their
cell walls. This is a long carbohydrate polymer that also
occurs in the exoskeletons of insects, spiders, and other
arthropods. The chitin adds rigidity and structural support
to the thin cells of the fungus, and makes fresh mushrooms
crisp. ]
Unique features:
 Some species grow as single-celled yeasts that
reproduce by budding or binary fission.
 Shared features:
 With other eukaryotes: As other eukaryotes, fungal cells
contain membrane-bound nuclei with chromosomes that
contain DNA
 With plants: Fungi possess a cell wall and vacuoles.They
reproduce by both sexual and asexual.

21.  In common with some plant and animal species, more
than 60 fungal species display the phenomenon of
bioluminescence.
 grow in a wide range of habitats, including extreme
environments such as deserts or areas with high salt
concentrations or ionizing radiation, as well as in deep
sea sediments. Some can survive the intense UV and
cosmic radiation encountered during space travel.

22. A protist is any organism that is not
a plant, animal or fungus.

23. Characteristics of Protists
 mostly unicellular, some are multicellular (algae)
 can be heterotrophic or autotrophic
 most live in water (though some live in moist soil or even the human body)
 ALL are eukaryotic (have a nucleus)
Classification of Protists
 how they obtain nutrition
 how they move
 Animallike Protists - also called protozoa (means "first animal") - heterotrophs
 Plantlike Protists - also called algae - autotrophs
 Funguslike Protists - heterotrophs, decomposers, external digestion
 .Animallike Protists: Protozoans

24. Four Phyla of Animallike Protists
 Zooflagellates
move using one or two flagella
absorb food across membrane
 Sarcodines
moves using pseudopodia ( "false feet" ), which are like extensions
of the cytoplasm --ameboid movement
ingests food by surrounding and engulfing food (endocytosis),
creating a food vacuole
 Ciliates
Parameciummove using cilia
has two nuclei: macronucleus, micronucleuseproduces asexually (binary
fission) or sexually (conjugation)
outer membrane -pellicle- is rigid and paramecia are always the same
shape, like a shoe
 Sporozoans
do not move on their own
parasitic
Malaria is a sporozoan, infects the liver and blood