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Vaccinated individuals become protected against polio because the weakened
viruses promote production of antibodies.
Viruses require a host cell because they are not able to make proteins on their own.
Methanogens, thermophiles, and halophiles are some of the most primitive lifeforms found on Earth and thrive in very harsh environments. These unicellular,
prokaryotic organisms most likely belong to the kingdom archaebacteria.
prokaryotes are much smaller than eukaryotes
prokaryotes lack (do not have) nuclei
During an infection, some viruses remain inside cell but do not cause symptoms of
disease. The graphic above depicts the lysogenic cycle in which cell and viral DNA
are copied.
examples of negative feedback:
When an athlete is working out their body sweats and blood vessels dilate to
lower the body temperature until it returns to average
The body detects the amount of sugar in the blood and secretes the hormone
insulin to keep the sugar at a manageable amount
The Nervous and endocrine systems work together to monitor and control response
to internal and external stimuli
Certain reactions, like when you touch something hot and pull away quickly, are
not processed in the brain, but rather between motor neurons. This action that
bypasses the brain is called a reflex arc.
At the base of the brain, connected to the spinal cord, is one of the most important
parts of the brain. In charge of vital functions like breathing and heartbeat, life is
not possible without the medulla oblongata.
Nitrogen is a key element in the body. It is used in everything from messengers
that relax the muscles to DNA and proteins. Nitrogen is not readily available in
forms the body can use in the air like oxygen is. Animals get the nitrogen that they
need when bacteria fix the nitrogen so plants can absorb it and animals eat the
plants.
When bacteria reproduce, they create two new copies of the original cell. Bacteria,
however, are regularly used in experiments testing evolution. Bacteria end up with
differing DNA through a process called conjugation.
Bacteria come in many different shapes and combinations:
Combination:
two = diplo
strings = strepto
clumps = staphylo
Shapes:
Rod = bacilli
Round = coccus
Spiral =spirilla
Top picture is streptococcus
Bottom picture is staphylococcus
The integumentary system is the body's first defense against infection as well as a
way to release wastes from the body. The outer layer of this system that contains
keratin and melanin is known as epidermis.
Sensory neurons pick up information about the world around an organism and
transmit it to the brain. These specialized cells have a specific shape that allows
them to be quick and efficient. This is a neuron:
Characteristics of bacteria:
The oldest life-forms on earth
Move, grow, and reproduce on their own
Organisms evolved from these
Characteristics of viruses:
Exhibit characteristics of non-living things
Need a host cell to carry out metabolic functions
Surrounded by a protein coat
Characteristics of the nervous system:
Made up of the central and peripheral systems
Sends electrical messages throughout the body
Characteristics of the endocrine system:
Uses hormones to send messages throughout the body
Made up of glands that secrete chemical messages