Download Middle School Science Room 212 – Miss Lida Lesson 1 – Explore

Middle School Science
212 – Miss Lida
Room
Lesson 1 – Explore – Page 279
“What Are Animals?”
Animal Characteristics
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All animals, like plants, are multi-cellular.
While cell walls support plant cells, a protein called collagen holds animal
cells together.
Animals are the only living things that have nerve cells.
Most animals also have muscle cells that help them move.
All animals get energy from the food they take into their bodies.
All animals begin as a fertilized egg cell called a zygote.
How Do Scientists Group Animals?
Symmetry
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One way to group animals is by looking at their symmetry, or how body parts
are arranged.
The three types of symmetry are:
1. bilateral symmetry – a body plan in which an
organism can be divided into two parts that are
nearly mirror images of each other. (Examples are:
humans, frogs, and geckos)
2. radial symmetry – a body plan which can be
divided into two parts that are nearly mirror images
of each other anywhere through its central axis.
3. asymmetry – body plans which cannot be divided
into any two parts that are nearly mirror images.
Groups of Animals
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Scientists use a system called taxonomy to organize living things. Because
each animal cell has a nucleus at some point in its life, animals are in the
Domain Eukarya.
The next level consists of the kingdom taxons.
Scientists use certain traits to determine whether an organism belongs in the
kingdom Animalia. Animals then are classified into phylum, genus, and
species.
Family Tree
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A family tree shows the relationships among and within generations of a
family.
Animal phyla are also organized by how they are related through time.
Animal Adaptation
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An adaptation is an inherited trait that increases an organism’s chances of
surviving and reproducing in its environment.
Structural Adaptation
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Animal species have structural adaptations that include their senses,
skeletons, and circulation.
Animals’ skeletons have evolved into three different types to support their
bodies:
1. An earthworm has a hydrostatic skeleton, a fluid-filled internal cavity
surrounded by muscle tissue.
2. A crab has soft internal structures. The structures are protected by a
thick, hard outer covering, called an exoskeleton.
3. The internal, rigid framework that supports you and other animals is
called an endoskeleton. Your endoskeleton is made of bone.
Animal species also have structural adaptations for circulating blood. (For
example, ants have an open circulatory system which means that an ant’s
heart pumps blood into open spaces around its organs.
An earthworm however, has a closed circulatory system.
Many hearts pump blood through a system of vessels.
Other animals with closed circulation have only one heart.
Behavioral Adaptations
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Animals are born with behaviors called instincts. These behaviors have
evolved over time and help species survive in their environments.
The ability to learn behaviors also is an important animal adaptation. For
example, young songbirds learn how to sing their songs by listening to their
parents. Baby geese also learn to follow their mothers soon after birth. This
form of learned behavior is called imprinting.
Functional Adaptations
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Animal species also have functional adaptations, which enable them to
increase survival or maintain homeostasis.
Most animals that live in water release large numbers of eggs or sperm. If
fertilization occurs in the water, the process is called external fertilization. If
fertilization occurs inside a female, it is called internal fertilization.
Most animal species that live on land use internal fertilization. Because the
eggs are inside a female, only a few eggs need to be produced to ensure
survival of the young.