What is an Animal? Chapter 25

Characteristics of Animals Animals are: eukaryotic, multi- cellular organisms with ways of moving that help them reproduce, obtain food, and protect themselves.

Methods for Obtaining Food All animals are heterotrophic – they obtain energy & nutrients from outside sources. (autotrophs)

Examples Frogs & Birds can move to search for food Barnacles remain stationary

Sessile – a method Organisms that are permanently attached to a surface are called sessile Some aquatic animals, such as corals and sponges move about only during the early stages of their lives

Digest Food Animals must digest or break down their food once consumed Some digest: internal cavity example: monkey, earthworm, frogs…

Some do it this way… Sponges & Flatworms digest within individual cells

Section 25.1 Summary – pages Animals digest food In animals such as planarians and earthworms, food is digested in a digestive tract. Mouth Anus Digestive tract Extended pharynx

Digestive Track of the Earthworm & Flatworm Earthworms ingest soils & digest the matter contained in it They have 2 body openings Several structures for storing, grinding or dissolving food Food travels along one path with 2 openings Flatworm only has 1 opening Feeds on small, living organism or dead bodies of larger animals

Development of Animals Most animals develop from a fertilized egg cell called a zygote After fertilization, developmental stages take place

Blastula When the zygote divides into 2 cells it is called cleavage The 2 cells that resulted from cleavage then divide into 4 cells …then a cell-covered fluid-filled ball called the blastula Picture of Sea Urchins Forming Into Blastula Embryonic Cells

CLEAVAGE

Gastrula After the blastula forms, the cells on one side of the blastula then move inward to form the gastrula This structure is made of 2 layers of cells w/ an opening at one end. Endoderm (Inner Surface) Ectoderm (Outer Surface)

Formation of the Mesoderm The Mesoderm is the 3 rd cell layer found in the embryo between the ectoderm & endoderm. Develops into muscles, circulatory system, excretory system, & respiratory system

Section 25.1 Summary – pages 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

Formation of Mesoderm An animal whose mouth developed not from the opening, but from cells elsewhere on the gastrula is called a deuterostome

Section 25.1 Summary – pages Fertilization First cell division Additional cell divisions Cell Differentiation in Animal Development Formation of a blastula Gastrulation Formation of mesoderm Sperm cells Egg cell Endoderm Mesoderm Ectoderm

Growth & Development Most embryos continue to develop and resemble the adult Some embryos develop into a larva Sea Urchin Larva Adult Sea Urchin

Body Plans & Adaptations Section 2

What is symmetry? Each animal has a different shape or form because each have a different symmetry Symmetry refers to a balance in proportion Different symmetry helps an animal move & find food 3 types of Symmetry 1. Asymmetry 2. Radial Symmetry 3. Bilateral Symmetry

Asymmetry Most sponges live on the bottom of the ocean & have irregular shaped bodies They exhibit asymmetry b/c they do not have a equal division body plan

Sponges Consist of 2 layers of cells Outer layer protects from predators Inner layer keeps water moving for digestion Sponges 1 st evolved ~600 mya & represent one of the oldest groups of animals on earth!

Radial Symmetry Radial symmetry is animals that can detect & capture prey coming toward any direction Animals can be divided along any plane

Hydra Hydra is a tiny predator that feeds on small animals with its tentacles It is radial symmetry The tentacles radiate out from around its mouth

Bilateral Symmetry Can be divided down its length into similar right & left haves to form mirror images of one another Body Portions consist of: 1.Anterior: head end 2.Posterior: Tail end 3.Dorsal: Back surface 4.Ventral: Belly Surface

Body Portions ANTERIOR POSTERIOR DORSAL VENTRAL

Body Plans Body cavities make it possible for animals to grow, move, & feed Acoelomate: animal's with 3 cell layers with a digestive tract but no cavities Flatworms Ectoderm Mesoderm Endoderm Body cavity Digestive tract

Section 25.2 Summary – pages Pseudocoelomates A roundworm is an animal with bilateral symmetry. The body of a roundworm has a space that develops between the endoderm and mesoderm. Ectoderm Mesoderm Endoderm Body cavity Digestive tract Pseudocoelomate Roundworm

Section 25.2 Summary – pages Coelomates The body cavity of an earthworm develops from a coelom, a fluid-filled space that is completely surrounded by mesoderm. The greatest diversity of animals is found among the coelomates. Ectoderm Mesoderm Endoderm Body cavity Digestive tract Coelomate Segmented Worm Coelom

Animal Protection & Support Exoskeleton: a hard, waxy covering on the outside of the body that provides a framework for support Prevents water loss Provides place for muscle attachment Nymph

Animal Protection & Support Endoskeleton: internal skeleton that provides framework within the body Animals have a backbone Protects internal organs

Animal Protection & Support Vertebrate is an animal with an endoskeleton and a backbone

Animal Protection & Support Invertebrate is an animal that does not have a backbone