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Chapter 27: Introduction to Animals

Chapter 27: Introduction to Animals. Section 2: Animal Body Systems. Tissues and Organs. Digestion Single celled organisms and sponges digest their food within their body cells.

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Chapter 27: Introduction to Animals

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  1. Chapter 27: Introduction to Animals Section 2: Animal Body Systems

  2. Tissues and Organs • Digestion • Single celled organisms and sponges digest their food within their body cells. • All other animals digest their food extracellularity (outside of their body cells) within a digestive cavity.

  3. Tissues and Organs • Simple animals, such as the hydra and flatworms, have a gastrovascular cavity, a digestive cavity with only one opening.

  4. Tissues and Organs • Other animals have a digestive tract (gut) with two openings, a mouth and an anus.

  5. Tissues and Organs • Respiration • In simple animals, oxygen gas and carbon dioxide gas are exchanged directly with the environment by diffusion.

  6. Tissues and Organs • The uptake of oxygen and the release of carbon dioxide, called respiration, can take place only across a moist surface.

  7. Tissues and Organs • Some aquatic (and a few terrestrial) animals respire with gills – very thin projections of tissue that are rich in blood vessels. Gills

  8. Tissues and Organs • In more advanced animals, lungs are the respiratory organs used to transfer oxygen into the blood and remove carbon dioxide from blood.

  9. Tissues and Organs • Circulation • In complex animals, oxygen and nutrients must be transported to the body cells by a circulatory system.

  10. Tissues and Organs • Two types of circulatory systems: • Open circulatory system: heart pumps fluid containing oxygen and nutrients through a series of vessels out into the body cavity.

  11. Tissues and Organs • Closed circulatory system:a heart pumps blood through a system of blood vessels.

  12. Tissue and Organs • Conduction of Nerve Impulses • Nerve cells (neurons) are specialized for carrying messages in form of electrical impulses. • Bilaterally symmetric animals have clusters of neurons called ganglia.

  13. Tissue and Organs • More complex invertbrates, such as the grasshopper, have brains with sensory structures.

  14. Tissue and Organs • Support • Many soft-bodied invertebrates have a hydrostatic skeletal systems. • Hydrostatic skeleton - consists of water that is contained under pressure in a closed cavity.

  15. Tissue and Organs • Other invertebrates, such as insects, have an exoskeleton, which is a rigid external skeleton that encases the body of an animal.

  16. Tissue and Organs • An endoskeleton is composed of a hard material, such as bone, embedded within an animal.

  17. Tissue and Organs • Excretion • The term excretion refers to the removal of wastes produced by cellular metabolism.

  18. Tissue and Organs • Simple aquatic invertebrates and some fishes excrete ammonia into the water through their skin or gills by diffusion.

  19. Tissue and Organs • Other animals, especially terrestrial animals, convert ammonia to nontoxic chemicals, like urea. • As the excretory system eliminates these wastes, water and other useful substances are returned to the body.

  20. Reproductive Strategies • Asexual Reproduction • Reproduction that does not involve the fusion of two gametes is called asexual reproduction. • An unusual method of asexual reproduction is parthenogenesis, in which a new individual develops from an unfertilized egg.

  21. Reproductive strategies • Animals that reproduce asexually are usually able to also reproduce sexually.

  22. Reproductive Strategies • Sexual Reproduction • In sexual reproduction, a new individual is formed by union of a male and a female gamete.

  23. Reproductive Strategies • Gametes are produced in the sex organs. • Males have testes that produce sperm. • Males produce sperm until death.

  24. Reproductive Strategies • Females have ovaries that produce eggs. • At birth, females have produced all the eggs they will ever have.

  25. Reproductive Strategies • Some species of animals, called hermaphrodites, have both testes and ovaries.

  26. Reproductive Strategies • Most aquatic animals simply release the male and female gametes near one another in the water, where fertilization occurs. • This is known as external fertilization.

  27. Reproductive Strategies • Most terrestrial animals sexually reproduce by means of internal fertilization. • Internal fertilization occurs when the sperm and egg unite inside of the female’s body.

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