Chapter 25: What is an Animal? 25.1: Typical Animal Characteristics

25.1 Vocabulary Autotroph Sessile Blastula Gastrula Ectoderm Endoderm Mesoderm Protostome Deurterostome

Characteristics of Animals Eukaryotic Multicellular Move to aid in reproduction, obtaining food and protection. Most have specialized cells that form tissues and organs (nerves and muscles) No cell wall

Animals Obtain Food All animals are heterotrophs Some animals move to obtain food while others do not. Organisms that are permanently attached to a surface are called sessile.

Animals Obtain Food Aquatic animals do spend some of the early stages of their life cycle moving when they hatch from fertilized eggs into free-swimming larval forms. Most adults are sessile and attach themselves to rocks or other objects. Land animals expend more energy and use more oxygen to search for food.

Animals Digest Food After animals ingest their food they must digest it. Some animals carry out digestion in individual cells; while others have an internal cavity where digestion takes place. Some of this food is stored as fat or glycogen and used when food is not available.

Animals Cell Adaptations Most animal cells are differentiated and carry out different functions. There are specialized cells for sense and seeking food and mates, and to allow them to identify predators.

Development of Animals Most animals grow and develop from fertilization (zygote). How does a snail with many different specialized cells grow from a zygote? Zygotes of different animals species all have similar, genetically determined stages of development

Fertilization Most animals reproduce sexually Male animals produce sperm cells Female animals produce egg cells Fertilization occurs when an sperm cell penetrates the egg cell, forming a zygote. Fertilization can be internal or external

Cell Division Once the zygote forms, mitosis occurs and two cells form. Once cell division begins the organisms in known as an embryo. The two cells divide into four cells and so on, until a cell-covered, fluid filled ball is formed called a blastula.

Cell Division Problem-Solving Lab 25.1 pg. 676 You will determine that cytoplasm differences can influence development in frogs. The normal pattern of cell division occurs as shown in the diagram on the left. The last phase shown in both diagrams shows the larval stage of frog development.

Gastrulation After blastula formation, cell division continues. The cells on one side of the blastula then move inward to form a gastrula– a structure made up of two layers of cells with an opening at one end. The cells at one end of the blastula move inward, forming a cavity lined with a second layer of cells.

Gastrulation The layer of cells on the outer surface of the gastrula is called the ectoderm. The ectoderm will continue to grow and divide and develop into skin and nervous tissue of the animal.

Gastrulation The layer of cells lining the inner surface is called the endoderm. The endoderm cells develop into the lining of the animals digestive tract and into organs associated with digestion.

Formation of Mesoderm The process of gastrulation continues until a layer of cells called the mesoderm forms. “meso” = “middle” Mesoderm is found in the middle of the embryo The mesoderm is the 3rd layer found in the developing embryo between the ectoderm and the endoderm.

Formation of Mesoderm Mesoderm cells develop into muscles, circulatory system, excretory system, and, in some animals, the respiratory system. Journal Drawing: Cell Differentiation in Animal Development pg. 678

Formation of Mesoderm When the opening in the gastrula develops into the mouth, the animal is called a protostome. Snails, earthworms, and insects are examples of protostomes.

Formation of Mesoderm In other animals, including humans, the mouth does not develop form the gastrula’s opening. Animals whose mouth does not develop from the opening, but from cells elsewhere on the gastrula is called a deuterostome.

Growth and Development As the embryo develop, cells continue to become differentiated and specialized to perform different functions. Most embryos continue to develop over time, becoming juveniles that look like smaller version of the adult.

Growth and Development In insects and echinoderms, the embryo develops inside an egg into a larva; which usually does not resemble the adult version. Once these organisms hatch they generally become sessile as adults (sea urchins)

Adult Animals Once the larval stage passes, most animals continue to grow and develop into adults. For insects this could take a few days or up to 14 years for some mammals. Eventually the animal reaches sexual maturity, mate and the cycle begins again.

Chapter 25: What is an Animal? 25.2: Body Plans and Adaptations

Vocabulary Gastrula Symmetry Radial symmetry Bilateral symmetry Anterior Posterior Dorsal Ventral Acoelomate Pseudocoelom Coelom Exoskeleton Invertebrate Endoskeleton Vertebrate

What is Symmetry? All animals can be described in terms of symmetry- a term that describes the arrangement of body structures Different kinds of symmetry enable animals to move in different ways.

Asymmetry An animals with no symmetry or an irregular shape is said to be asymmetrical. Asymmetrical animals are usually sessile that do not move from place to place.

Asymmetry Sponges are asymmetrical The bodies of sponges consist of two lyers of cells Sponges embryonic development does not include the formation of an endoderm and mesoderm, or a gastrula stages. They represent one o the oldest groups of animals on Earth.

Radial Symmetry Animals with radial symmetry can be divide along any plane, through a central axis, into roughly equal halves. Hydra have radial symmetry.

Radial Symmetry Radial symmetry is an adaptation that enables an animal to detect and capture prey coming toward it from any direction.

Bilateral Symmetry Bilateral Symmetry: can be divided down its length into similar right and left halves. Can only be divided along one plane. Radially symmetrical animals can be divided along any vertical plane.

Bilateral Symmetry Bilateral animals have… Anterior: head end (often has sensory organs) Posterior: tail end Dorsal: upper surface Ventral: lower surface In upright animals the dorsal surface is the back and the ventral surface is the front (belly)

Problem-Solving Lab 25.2 Determine patterns of symmetry and their association with other traits. Pg. 682 In Class

Bilateral Symmetry and Body Plans All bilaterally symmetrical animals develop from three embryonic cell layers- Ectoderm Endoderm Mesoderm Some have fluid-filled space inside their bodies called cavities in which internal organs are found. Fluid-filled cavities made it possible for animals to grow larger because it allowed for the efficient circulation and transport of fluids and support for organs and organ systems.

Acoelomates Acoelomate: animals that develop from the three cell layers, but have no body cavities. They have a digestive tract that extends throughout the body. Example: Flatworms

Pseudocoelomate Pseudocoelom: fluid-filled body cavity partially lined with mesoderm that develops between the endoderm and mesoderm. Example: Roundworms Move quickly because its muscles attach to the mesoderm and brace against the pseudocoelom.

Pseudocoelomate Pseudocoelomates have a one-way digestive tract that has regions with specific functions. The mouth takes in food, the breakdown and absorption of food occurs in the middle section, and the anus expels wastes.

Coelomates Coelom: a fluid-filled space that is completely surrounded by mesoderm. Examples: humans, insects, and fishes. The greatest diversity of animals is found among coelomates.

Coelomates Specialized organs and organ systems develop in the coelom. The digestive tract and other internal organs are attached by double layers of mesoderm and are suspended within the coelom Like the pseudocoelom, the coelom cushions and protects internal organs. It provides room for them to grow and move independently within an animals body

Animal Protection and Support Animals have adaptations that allow them to survive in many different environments. Exoskeleton: a hard covering on the outside of the body that provides a framework for support.

Animal Protection and Support Exoskeletons also protect soft body tissue, prevent water loss, and provide protection from predators. It is secreted by the epidermis and extends into the body and as animals grow they secrete new ones and shed old ones.

Animal Protection and Support Exoskeletons are often found in invertebrates. Invertebrate: an animal that does not have a backbone Example: crabs, spiders, beetles

Animal Protection and Support Invertebrates, such as sea urchins and sea stars, have an internal skeleton called and endoskeleton. Endoskeleton: internal skeleton; provides support, protects internal organs, and acts as an internal brace for muscles to pull against.

Animal Protection and Support Endoskeletons can be made of calcium carbonates in sea stars; cartilage in sharks; or bone Bony fishes, amphibians, reptiles, birds and mammals have endoskeletons made of bone.

Animal Protection and Support Vertebrate: animal with an endoskeleton and a backbone. All vertebrates are bilaterally symmetrical.