Section 1: Characteristics of Animals
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Transcript of Section 1: Characteristics of Animals
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Section 1: Characteristics of Animals
Chapter 27: Introduction to Animals
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General Features of Animals Heterotrophy
Animals are heterotrophs – that is, they can not make their own food.
Most animals move from place to place searching for food.
Once food is located, it is eaten and then digested in a cavity inside the animal’s body.
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General Features of Animals
Mobility Animals are unique
among living things in being able to perform rapid, complex movements.
Animals move by means of muscle cells, specialized cells that are able to contract with considerable force.
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General Features of Animals
Animals can swim, crawl, walk, run, and even fly. In fact, flight has
evolved four times among animals , in insects, pterosaurs, birds and
bats.
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General features of Animals
• Multicellularity• All animals are
multicellular.• In spite of
differences in body size, there is little difference in the size of most cells that make up these animals
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General Features of Animals The cells on the
skin of your hand are roughly the same size as the cells in the heart of a whale or in the wing of a hummingbird.
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General Features of Animals Diploidy
With few exceptions, animals are diploid, meaning adults have two copies of each chromosome, one inherited from their father and one from their mother.
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General Features of Animals Only their gametes
(egg and sperm) are haploid.
A great advantage of diploidy is that it permits an animal to exchange genes between the two copies of a set of chromosomes, creating new combinations of genes.
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General Features of Animals
Sexual Reproduction Almost all animals reproduce
sexually by producing gametes, as do many plants, fungi, and protists.
The females’ egg cells are much larger than the males’ sperm cells.
Unlike the egg cells, the sperm cells of animals have a flagella and are highly mobile.
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General Features of Animals
Absence of a Cell Wall Among the cells of
multicellular organisms, only animal cell lack rigid cell walls.
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General Features of Animals The absence of a rigid cell wall has
allowed animals mobility that other multicellular organisms do not have.
You may not realize this, but there are cells moving in your body at all time.
Cells called macrophages, for example, act as mobile garbage collectors, crawling over tissues and removing debris.
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General Features of Animals
Blastula Formation In all animals
except sponges, the zygote (fertilized egg cell) undergoes cell division that form a hollow ball of cells called a blastula.
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General Features of Animals Cells within the blastula
eventually develop into three distinct layers of cells – ectoderm, endoderm, and mesoderm.
These layers are called the primary tissue layers because they give rise to all of the tissues and organs of the adult body.
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Origin of Animal Tissues and Organs
Primary Tissue
Gives rise to:
EctodermOuter layer of skin; nervous system; sense organs, such as eyes
EndodermLining of the digestive tract; respiratory system; urinary bladder; digestive organs; liver; many glands
MesodermMost of the skeleton; muscles; circulatory system; reproductive organs; excretory organs
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Gastrulation
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General Features of Animals Tissues
The cells of all animals except sponges are organized into structural and functional units called tissues.
Tissues are group of cells with a common structure that works together to perform a specific function
NO tissues
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Body Symmetry
All animals have their own particular body plan, a term used to describe an animal’s shape, symmetry, and internal organization.
An animal’s body plan results from a pattern of development programmed into the animal’s genes by natural selection
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Body Symmetry
Sponges have the simplest body plan of all animals.
Sponges are asymmetrical – irregular in shape and sometimes their shape depends on where they are growing.
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Body Symmetry
Animals with radial symmetry have body parts arranged around a central axis – like the spokes on a wheel.
Most are aquatic organisms.
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Body Symmetry
The bodies of all other animals show bilateral symmetry – body design with distinct right and left halves that are mirror images.
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Body Symmetry
Most bilaterally symmetrical animals have evolved an anterior concentration of sensory structures and nerves, a process called cephalization.
Anterior
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Internal Body Cavity Bilaterally
symmetrical animals have one of three basic kinds of internal body plans: Coelomates: body plan
that includes a body cavity – a fluid filled space found between the body wall and the digestive tract.
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Internal Body Cavity
Acoelomates – animals with no body cavity.
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Internal Body Cavity
Pseudocoelomates – Animals that have a body cavity located between the mesoderm and endoderm.
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3 Types of Body Plans
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Body Segmentation
Segmented animals are composed of a series of repeating, similar units called segments.
Segmentation underlies the organization of all advanced animals and is easy to observe in some animals, such as ants and earthworms.
ABDOMEN
THORAX
HEAD
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Body Segmentation
In vertebrates, segments are not visible externally, but there is evidence of segmentation in a vertebrate embryo.
HEAD
THORAX
ABDOMEN
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Kinds of Animals
Kingdom Animalia contains about 35 major divisions called phyla depending on how certain organisms are classified.
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Kinds of Animals
To visually represent the relationships among various groups of animals, scientists often use a type of branching diagram called a phylogenetic tree. A phylogenetic tree
shows how animals are related through evolution.
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Two Groups of Animals
The animal kingdom is divided into two groups of organisms:1. Vertebrates – animals
with backbones – humans, dogs, sharks
2. Invertebrates – animals without backbones – slugs, spiders, jellyfish