ASA
Chapter 1
Characteristics of Living Things
ALABAMA 7TH GRADE SCIENCE STANDARDS COVERED IN THIS CHAPTER INCLUDE:
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Describe characteristics common to living things, including growth and
development, reproduction, cellular organization, use of energy, exchange of
gases, and response to the environment.
CHARACTERISTICS OF LIFE
All living things, also called organisms, share the following seven characteristics:
1. Cells: Cells make up all living things.
Cells can sometimes organize into com
plex structures. Multicellular organisms
have many cells, and unicellular organisms have only one cell. Organisms can
be unicellular or multicellular.
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2. Sensitivity: Organisms respond to
figure 1.1 Cell
change in the environment. Responses
are reactions to changes in the environment. Plants can respond to the
environment by growing toward light sources or shedding leaves in winter.
Animals can respond to environmental change by hibernating or by fleeing
from predators. Responses occur many times in the life of one organism.
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Characteristics of Living Things
3. Growth: Organisms change over their lifetime.
Organisms get bigger in size as they grow from infancy
to adulthood. Highly intelligent animals, like humans,
learn many life skills during the growth of childhood.
Organisms may develop new structures or behaviors as
they age. Think of all the ways you have grown over the
years. You have gotten taller and increased body size.
You have gained experiences, knowledge and maturity.
All organisms show an increase in physical and mental
maturity the closer they come to reaching adulthood.
4. Homeostasis: Organisms must maintain an internal
environment that is suitable for life. Homeostasis is the
ability of an organism to keep a steady internal state.
Living things need the correct amount of fluids, salts,
hormones and food sources in order to survive. Also, Figure 1.2 Growing Up
more importantly, animals must maintain a suitable
internal temperature. Muscles that are too cold will not function. Specialized
body parts, like nerves, can easily be damaged by prolonged hot or cold
temperatures. This is one reason fevers can cause deafness, blindness and
paralysis.
5. Reproduction: All living things must be
able to reproduce. Organisms can reproduce
sexually or asexually. Sexual reproduction
occurs when two organisms create offspring,
and asexual reproduction occurs when one
organism is capable of creating offspring by
itself.
6. Metabolism: Organisms must get energy
Figure 1.3 Baby Snakes Hatching
from the environment and use the energy
they obtain to live. Metabolism is the sum of all chemical reactions within an
organism. Metabolism is how organisms are able to get and use energy. When
you eat food, metabolism is how your body is able to break down the food and
provide energy for your cells. All the cells in your body need energy to keep
your body alive and functioning. Exchanging gases, like when you breathe, is
also considered part of metabolism.
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Chapter 1
7. Adaptation: Over time, organisms can
become specially suited to a particular
environment. Sea turtles have long,
flipper-like legs and cannot easily walk
on land. They are adapted to living in the
ocean. Adaptations occur slowly, over the
course of many generations. Remember:
adaptations occur to populations of
organisms, not to the individual
organisms themselves.
Figure 1.4 Sea Turtle
VIRUSES ARE DIFFERENT FROM LIVING THINGS
You’ve heard ofthe flu, haven’t you? The flu is an illness caused
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by the influenza virus. It passes easily from person to person.
;NKS You may think a virus is a living thing because it can be
transmitted by living things. But in fact, a virus is not a living
ABCO5O
virus
thing. A virus particle cannot eat, and it can only reproduce
inside a cell. Outside a cell, a virus does nothing and remains
inactive. So what is it? A virus is a small particle that contains proteins and hereditary
material (DNA or RNA), but it is not alive. The virus is surrounded by a protein coat.
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Capsid
DNA
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Figure 1.5 Virus Particle
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Characteristics of Living Things
ORGANISMS MODIFY THEIR ENVIRONMENT
Humans change their environment. You can probably name many ways human
s change
their environment. Try to think ofsome now. Did you think ofthings like buildin
g roads
and neighborhoods, damming rivers or creating pollution? These are just
a few ways
that humans change their surroundings. Did you know almost all other organi
sms also
change their environment?
Think about it. Fungi and bacteria break down dead plants and animals
into basic
chemical components. Without these important recyclers, the Earth would
become
buried under mountains of waste. Here is another example: plants provid
e shade for
animals and other plants. Shade lessens the amount ofsunlight available to
other plants.
This changes the pattern of growth in the shaded area.
Some plants also change the air. These plants (with the help of bacteria) take
nitrogen
from the air and put it in the soil so other plants can use it. Can you think of anothe
r way
plants can alter the chemicals found in the air? Here’s a hint: think photosynthes
is!
Many animals also modify environments. Beavers build dams (Figure 1 .6). These
dams
create ponds or swamps where meadows once stood. The creation of a pond
is helpful
to beavers and fish. However, to mice and grass that once lived in the meado
w, the
creation of a new pond is harmful. It all depends on your perspective. Without
a doubt,
all plants and animals change their environment in some way.
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Figure 1.6 Organism Modifies Its Environment
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Chapter 1
Activity
Examine the description ofeach organism below. Then in the space provided, predict the
impact of that organism on the environment.
Organism
Description
Earthworm
Invertebrate worm that moves through the soileating
organic matter and leaving behind waste high in
nitrogen.
Termite
Invertebrate insect that consumes dead wood.
Clostridium Bacteria that live in the soil and water, breaks down
animal wastes.
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Lichen
Symbiotic fungi and algae that live on the surface of
rocks. Usually first organism to inhabit an area
following glacial retreat or volcanic eruption.
Herring
Vertebrate animal that lives in large schools and
consumes vast quantities of plankton.
Kudzu
A non-native species of plant introduced in 1876 to
reduce soil erosion. Now named a pest weed, kudzu
is actively destroyed by farmers and government
agencies.
Rabbit
Vertebrate mammal that lives in deciduous forests
and grasslands. Consumes grasses and small shrubs
and other vegetation.
Grasses
Vascular plant that requires high amounts of sunlight.
Grows quickly and reproduces several times in a
single season, producing many seeds.
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Black racer A fast moving vertebrate reptile found in grasslands
and forests alike. Its keen eyesight allows it to eat
snake
rodents, frogs and small lizards.
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Broadleafdeciduous tree found in a hardwood forest.
BONUS:
Sugar Maple Utilizes photosynthesis to convert solar energy to
cellular energy. Sugars found in fall leaves prevent
germination of similar seeds. This helps keep maple
trees from growing too close to each other
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Environmental
Impact
Characteristics of Living Things
CHAPTER
1 REVIEW
1. What statement does NOT correctly describe living things?
A
B
C
B
They must grow.
They use sexual reproduction.
They use metabolism.
They are made of cells.
2. Which statement below correctly describes an organism’s response to
environmental stimuli?
A
B
C
B
3.
Water in a rain cloud freezes into snow.
Solar radiation heats the soil to create wind.
Flowers bloom in springtime.
In a desert, evaporating water leaves behind salts.
Which statement correctly describes a metabolic process?
A
B
C
B
Animals take in oxygen for cellular respiration.
Sea turtles come ashore only to lay eggs.
Baby orangutans learn from their mothers to build tree nests.
Adult male lions roar to protect their home territory.
4. Which characteristic listed below is common to all living organisms?
A
B
C
D
is able to move
uses sunlight to trap energy
reproduces using eggs
maintains homeostasis
5. Learning to dance is an example of what characteristic of living things?
A
B
C
B
response to environmental stimuli
growth and development
metabolism
cellular organization
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