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Life Processes &
Homeostasis
Life Processes & Homeostasis
KEY IDEA #1 - Living things are both
similar to and different from each other and
nonliving things.
KEY IDEA #2 - Organisms maintain a
dynamic equilibrium that sustains life.
Introduction
Living things are similar in that they rely on many of the same processes to stay alive, yet living things
are diverse (different) in the ways that these processes and interactions are carried out.
Nonliving things lack certain features found in living things, such as the ability to maintain cellular
organization, carry out metabolic processes while maintaining stability (homeostasis), and pass on
hereditary information through reproduction.
The components of living systems, from a single cell to an ecosystem, must work together to
maintain balance. To successfully accomplish this, organisms possess a diversity of regulatory
mechanisms that function to maintain the level of organization necessary for life. Diversity is important
at many levels of organization -- from a single cell to a multicellular organism, to an ecosystem.
Life is also dependent upon the availability of an energy source and raw materials that are used
in the basic enzyme-controlled biochemical processes of living organisms. These biochemical processes
occur within a narrow range of conditions. Because organisms are continually exposed to changes in
their external and internal environments, they must continually monitor and respond to these changes.
Responses to change can range in complexity from simple activation of a cell’s chemical processes to
learned behavior. The result of these responses is called homeostasis, a “dynamic equilibrium” or
“steady state,” which keeps the internal environment within certain limits. Organisms have a diversity of
homeostatic feedback mechanisms that detect deviations from normal and take corrective actions to
return their systems to normal range. Failure of these control mechanisms can result in disease or even
death.
Life Processes & Homeostasis
Key Concepts
Part 1. Life Processes
* Biology is the study of living things, which are called
organisms.
* All living things share certain characteristics that
distinguish them from nonliving things.
* Living things are highly organized and contain many
complex chemicals.
* All living things contain one or more cells, use energy,
have a definite form, and a limited life span.
* Living things grow, respond to changes in the
environment, reproduce, and change over time.
* Some things, such as a virus, are difficult to classify
as either living or nonliving because they have many of
the characteristics of life. However, viruses DO NOT
are not cells, therefore they are considered to be
nonliving. A cell, therefore, is the basic unit of life.
* The function of many life processes is the maintain
homeostasis, which is a stable internal environment
Regulation is the life process that works to maintain
homeostasis.
* All living things must be able to carry on all the
processes of life which collectively are referred to a
metabolism. The processes of life include: respiration,
reproduction, regulation, growth, excretion, nutrition,
transport, and synthesis.
* Reproduction is the creation of offspring. It may be
sexual (two parents) or asexual (one parent).
* Respiration is a biochemical process (chemical
reaction) that releases energy from glucose which is
then used by living things to power its activities.
Respiration can be aerobic (without oxygen), or
anaerobic (without oxygen).
* Growth is the result of the processes of synthesis
and assimilation. It results in an increase in size and/
or the number of cells present in an organism.
* Excretion is the life process that removes toxic
metabolic wastes from an organism. The removal of
feces is NOT excretion, rather it is called egestion,
which removes solid, non-metabolic wastes from an
organism.
* Nutrition refers to how an organism obtains its food.
Some organisms can make their own food and are
called autotrophs. Others cannot make their food and
must obtain food by the process of ingestion and are
called heterotrophs.
* Transport involves the movement and distribution of
materials into, out of, and through out an organism.
* Synthesis is a process that involves combining simple
substances into complex ones through chemical
processes. For example, plants take carbon dioxide
and water and chemically combine them into glucose
(sugar) through the process of photosynthesis.
* Metabolism includes all of the biochemical processes
occurring within a living organism. (RRRGENTS)
Key Concepts
Part 2. The Human Body
* Humans are multicellular organisms that carry out
the processes of life through the interactions of several
body systems. The organization in humans, from
smallest to largest is: cell, tissue, organ, organ
system.
* All systems of the body synthesize various materials.
For example, the immune system produces antibodies,
the endocrine system synthesizes hormones, the
skeletal system makes blood cells, and the
reproductive system makes sex cells (sperm/egg)
which are necessary to produce human offspring.
* The main functions of the digestive system is to
allow the intake (ingestion) of food, to break that food
down into smaller, usable nutrients (digestion), and to
absorb those nutrients into the bloodstream so they
can be transported to all the cells of the body.
* The main functions of the skeletal system are to
provide shape and support, store minerals, protect
internal organs, to produce blood cells in the bone
marrow, and to allow movement by working with the
muscular system.
* The muscular system is composed of three types of
muscle cells: smooth (non-striated), skeletal
(striated), and cardiac (striated). Smooth and cardiac
muscles are involuntary, while skeletal muscles
voluntary. The main job of the muscular system is to
allow movement.
* The main job of the respiratory system is to bring
oxygen into the body so that energy can be produced
by the process of aerobic cellular respiration. The
respiratory system allows the oxygen from the air to
diffuse into the red blood cells at the alveoli, while
carbon dioxide, a waste product of cellular respiration, diffuses out of the blood at the alveoli in the
lungs.
* The job of the circulatory system is to transport
materials such as oxygen, nutrients, hormones,
antibodies throughout the body. The circulatory system
also transports metabolic wastes to the lungs, kidneys,
skin, and liver so they can be removed from the
bloodstream by the excretory system.
* The immune system helps to protect the body from
disease and infectious agents such as bacteria, viruses,
fungi, known as pathogens. Antibodies are made to
defend against antigens, proteins on the pathogen’s
surface, which can trigger an immune response.
* The nervous system and the endocrine systems work
together to regulate the body in order to maintain
homeostasis. The nervous system consists of the
brain, spinal cord, and nerves which allow messages in
the form of electrical impulses to travel through the
body. The endocrine system sends messages
throughout the body too, but in the form of chemical
messengers called hormones which regulate overall
metabolism, as well as growth, and reproduction.
VOCABULARY
Biology
Cell
Organism
Homeostasis
Metabolism
Reproduction
Asexual Reproduction
Sexual Reproduction
Regulation
Respiration
Aerobic
Anaerobic
Hormones
Growth
Excretion
Nutrition
Autotroph
Heterotroph
Transport
Synthesis
Assimilation
Locomotion
Nutrients
Ingestion
Digestion
Ingestion
Key Concepts
Part 3. Homeostasis & Disease
* The systems of the body work together to maintain
homeostasis.
* A change in one system will result in a change in
another system. For example, when the muscles are
exercised, the circulatory system responds by
increasing the heart rate.
* Failure of the body to maintain homeostasis will result in
sickness, disease, and even death.
* The immune system is the body’s defense against
disease and infection.
* The body’s largest non-specific defense against
pathogens is the skin, which acts as a barrier.
* The inflammatory response is a non-specific
defense reaction too tissue damage caused by injury or
infection. It results in an increased flow of blood to the
affected area.
* Once the body has been exposed to a pathogen,
WBCs (white blood cells), will either engulf them by the
process of phagocytosis, or other specialized WBCs
will produce chemical called antibodies which will
destroy the pathogen. Antibodies are specific, meaning
they will only work on one type of pathogen.
* Malfunctions of the immune system include allergies,
autoimmune diseases, and AIDS.
* Active immunity results in permanent immunity by the
production of antibodies. Active immunity can be
brought about through a vaccination (dead or
weakened pathogen), or by exposure to the living
pathogen.
* Passive immunity is a temporary form of immunity
brought about by “borrowing” antibodies from another
source. For example, babies who are breastfed get
antibodies from their mother’s milk.
* Regulating homeostasis involves cells communicating
with other cells throughout the body. This is
accomplished through the action of special structures
called receptor molecules which are found on the
surfaces of cells. The receptor molecules have shapes
which are specific to the chemicals interacting with
them. For example, insulin is a hormone released by
the pancreas and is responsible for the regulation of
blood sugar (glucose) levels. Insulin receptors on each
cell’s surface “fit” the shape of insulin which then
allows the passage of glucose into each cell.
* There are two (2) basic mechanisms for maintaining
homeostasis: Negative Feedback and Positive
Feedback. (See pages 29-31 in your review book for
specific details.)
VOCABULARY
Active Immunity
AIDS
Allergies
Antigen
Antibodies
Autoimmune
Glucose
HIV
Inflammatory Response
Insulin
Negative Feedback
Organ
Pancreas
Phagocytosis
Positive Feedback
Passive Immunity
Receptor Molecules
Skin
Tissue
Vaccination