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Chapter 27: Introduction to Animals.  Heterotrophy  Animals are heterotrophs – that is, they can not make their own food.  Most animals move from place.

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Presentation on theme: "Chapter 27: Introduction to Animals.  Heterotrophy  Animals are heterotrophs – that is, they can not make their own food.  Most animals move from place."— Presentation transcript:

1 Chapter 27: Introduction to Animals

2  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.

3  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.

4  Animals can swim, crawl, walk, run, and even fly. In fact, flight has evolved four times among animals, in insects, pterosaurs, birds and bats.

5 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

6  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.

7  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.

8  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.

9  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.

10  Absence of a Cell Wall  Among the cells of multicellular organisms, only animal cell lack rigid cell walls.

11  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.

12  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.

13  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.

14 Primary TissueGives rise to: Ectoderm Outer layer of skin; nervous system; sense organs, such as eyes Endoderm Lining of the digestive tract; respiratory system; urinary bladder; digestive organs; liver; many glands Mesoderm Most of the skeleton; muscles; circulatory system; reproductive organs; excretory organs


16  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

17  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

18  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.

19  Animals with radial symmetry have body parts arranged around a central axis – like the spokes on a wheel.  Most are aquatic organisms.

20  The bodies of all other animals show bilateral symmetry – body design with distinct right and left halves that are mirror images.

21  Most bilaterally symmetrical animals have evolved an anterior concentration of sensory structures and nerves, a process called cephalization.

22  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.

23  Acoelomates – animals with no body cavity.

24  Pseudocoelomates – Animals that have a body cavity located between the mesoderm and endoderm.


26  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.

27  In vertebrates, segments are not visible externally, but there is evidence of segmentation in a vertebrate embryo.

28  Kingdom Animalia contains about 35 major divisions called phyla depending on how certain organisms are classified.

29  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.

30  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

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