Comparing Invertebrates Chapter 29

Invertebrate Evolution Chapter 29-1

Origins of Invertebrates 29-1 Invertebrate Evolution Origins of Invertebrates Early animals were flat, soft bodied organisms that lived on the bottom of shallow seas. Segmented with bilateral symmetry. NO cell specialization. Recently scientists discovered microscopic fossils that are 610-570 million years old. Seem to be developing embryos of early multi-cellular organisms. 3

The First Multicellular Animals 29-1 Invertebrate Evolution The First Multicellular Animals Ediacaran Fossils found in China 610 to 570 Million Years old They are the ancestors of today’s multicellular animals

The First Multicellular Animals 29-1 Invertebrate Evolution The First Multicellular Animals The fossils: were flat and plate shaped were segmented had bilateral symmetry lived on the bottom of shallow seas were made of soft tissues absorbed nutrients from the surrounding water

Invertebrate Phylogeny 29-1 Invertebrate Evolution Invertebrate Phylogeny Many features of modern invertebrates evolved during the Cambrian period such as: tissues and organs patterns of early development body symmetry cephalization segmentation formation of three germ layers and a coelom

Invertebrate Phylogeny 29-1 Invertebrate Evolution Invertebrate Phylogeny Invertebrate Evolutionary Relationships This diagram illustrates one recent theory about the phylogenetic relationships among groups of living animals.

Invertebrate Phylogeny 29-1 Invertebrate Evolution Invertebrate Phylogeny Roundworms Flatworms Cnidarians This diagram illustrates one recent theory about the phylogenetic relationships among groups of living animals. Labels indicate the evolution of major features such as radial symmetry. Sponges Unicellular ancestor

Invertebrate Phylogeny 29-1 Invertebrate Evolution Invertebrate Phylogeny This diagram illustrates one recent theory about the phylogenetic relationships among groups of living animals.

Invertebrate Phylogeny 29-1 Invertebrate Evolution Invertebrate Phylogeny This diagram illustrates one recent theory about the phylogenetic relationships among groups of living animals.

Invertebrate Phylogeny 29-1 Invertebrate Evolution Invertebrate Phylogeny Invertebrate Evolutionary Relationships This diagram illustrates one recent theory about the phylogenetic relationships among groups of living animals.

Evolutionary Trends Specialized cells, Tissues, and Organs 29-1 Invertebrate Evolution Evolutionary Trends Specialized cells, Tissues, and Organs Sponges - 1st with specialized cells Jelly fish - 1st with muscle tissue Flatworms - 1st with organs Body Symmetry Asymmetrical (no symmetry) – Sponges only Radial – Jellyfish and Echinoderms Bilateral – Flatworms, Roundworms, Annelids, arthropods, and Mollusks 12

29-1 Invertebrate Evolution Evolutionary Trends Cnidarians and echinoderms exhibit radial symmetry where parts extend from the center of the body. Radial symmetry Planes of symmetry

29-1 Invertebrate Evolution Evolutionary Trends Worms, mollusks, and arthropods exhibit bilateral symmetry, or have mirror-image left and right sides. Bilateral symmetry

Cephalization Evolutionary Trends 29-1 Invertebrate Evolution Evolutionary Trends Cephalization Cephalization is the concentration of sense organs and nerve cells in the front of the body. Invertebrates with cephalization can respond to the environment in more sophisticated ways than can simpler invertebrates. None: Sponges Nerve Net: Cnidarians Ganglia: Worms, Clams, Echinoderms Brains: Cephalopod Mollusks, Arthropods 15

Segmentation Evolutionary Trends 29-1 Invertebrate Evolution Evolutionary Trends Segmentation Over the course of evolution, different segments in invertebrates have often become specialized for specific functions. Segmentation allows an animal to increase its size with minimal new genetic material.

Coelom Formation Evolutionary Trends Acoelomate 29-1 Invertebrate Evolution Evolutionary Trends Coelom Formation  Flatworms are acoelomates. This means they have no coelom, or body cavity, that forms between the germ layers. Ectoderm Mesoderm Endoderm Acoelomates do not have a coelom, or body cavity, between their body wall and digestive cavity. Digestive cavity Acoelomate

29-1 Invertebrate Evolution Evolutionary Trends Pseudocoelomates have a body cavity lined partially with mesoderm. Pseudocoelom Pseudocoelomates have body cavities that are partially lined with tissues from mesoderm. Digestive tract Pseudocoelomate

29-1 Invertebrate Evolution Evolutionary Trends Most complex animal phyla have a true coelom that is lined completely with tissue derived from mesoderm. Coelom Most complex animal phyla are coelomates, meaning that they have a true coelom that is lined completely with tissues from mesoderm. Digestive tract Coelomate

29-1 Invertebrate Evolution Evolutionary Trends 20

Embryological Development 29-1 Invertebrate Evolution Evolutionary Trends Embryological Development   In most invertebrates, the zygote divides to form a blastula—a hollow ball of cells.

29-1 Invertebrate Evolution Evolutionary Trends In most worms and arthropods, nerve cells are arranged in structures called ganglia. In more complex invertebrates, nerve cells form an organ called a brain.

Evolutionary Trends 29-1 Invertebrate Evolution This table shows the major characteristics of the main groups of invertebrates. Germ layers, body symmetry, cephalization, and development of a coelom are more common in complex invertebrates than in simple ones. Mollusks, for example, have all of these features, but sponges have none of them.

Evolutionary Trends 29-1 Invertebrate Evolution This table shows the major characteristics of the main groups of invertebrates. Germ layers, body symmetry, cephalization, and development of a coelom are more common in complex invertebrates than in simple ones. Mollusks, for example, have all of these features, but sponges have none of them.

Invertebrate Form & Function Chapter 29-2

The End

29-2 Form and Function in Invertebrates Feeding and Digestion Intracellular: Food digested by cells and passed around by diffusion. (ex: sea anemone) Extracellular: food broken down in cavity and then absorbed. (ex: earthworm) 27

Feeding and Digestion Feeding and Digestion 29-2 Form and Function in Invertebrates Feeding and Digestion Feeding and Digestion The simplest animals break down food primarily through intracellular digestion. More complex animals use extracellular digestion.

29-2 Form and Function in Invertebrates Feeding and Digestion When food is digested inside cells, this process is known as intracellular digestion. Sponges use intracellular digestion.

29-2 Form and Function in Invertebrates Feeding and Digestion In extracellular digestion, food is broken down outside the cells in a digestive cavity or tract and then absorbed into the body. Mollusks, annelids, arthropods, and echinoderms rely almost entirely on extracellular digestion. Flatworms and cnidarians use both intracellular and extracellular digestion.

29-2 Form and Function in Invertebrates Feeding and Digestion Cnidarians and most flatworms ingest food and expel wastes through a single opening. Food is digested in a cavity through both extracellular and intracellular means.

Feeding and Digestion Cnidarian Flatworm 29-2 Form and Function in Invertebrates Feeding and Digestion Mouth/anus Gastrovascular cavity Cnidarians and flatworms have a digestive system with only one opening. In more complex animals, the digestive system has two openings. In addition, the digestive organs have become more specialized. Digestive cavity Cnidarian Pharynx Mouth/anus Flatworm

29-2 Form and Function in Invertebrates Feeding and Digestion In more-complex animals, food enters the mouth and wastes leave through the anus. A one-way digestive tract often has specialized regions.

Feeding and Digestion Annelid Arthropod 29-2 Form and Function in Invertebrates Feeding and Digestion Intestine Gizzard Crop Pharynx Annelid Mouth Anus Crop Pharynx Cnidarians and flatworms have a digestive system with only one opening. In more complex animals, the digestive system has two openings. In addition, the digestive organs have become more specialized. Anus Arthropod Mouth Stomach and digestive glands Rectum Intestine

Respiration All respiratory systems have two basic requirements: 29-2 Form and Function in Invertebrates Respiration All respiratory systems have two basic requirements: a large surface area that is in contact with the air or water the respiratory surfaces must be moist for diffusion to occur

Respiration Aquatic invertebrates: Require moist respiratory surfaces 29-2 Form and Function in Invertebrates Respiration Aquatic invertebrates: Require moist respiratory surfaces Some through the pores of the skin Some through gills (large feathery structure rich in blood vessels) Large surface area provides for greater absorption of oxygen. 36

Respiration Aquatic Invertebrates 29-2 Form and Function in Invertebrates Respiration Aquatic Invertebrates Gills are feathery structures that expose a large surface area to the water. Invertebrates have a variety of respiratory structures. Clams and other aquatic mollusks have gills.

Respiration Terrestrial Invertebrates: Covered by water or mucus 29-2 Form and Function in Invertebrates Respiration Book Lungs Terrestrial Invertebrates: Covered by water or mucus inside the body. Book lungs – spiders Spiracles - other insects Spiracles 38

Respiration Terrestrial Invertebrates 29-2 Form and Function in Invertebrates Respiration Terrestrial Invertebrates Grasshoppers and other insects have spiracles and tracheal tubes. Invertebrates have a variety of respiratory structures. Grasshoppers and other insects have spiracles and tracheal tubes. All respiratory organs have large, moist surface areas in contact with air or water.

29-2 Form and Function in Invertebrates Circulation Most complex animals have one or more hearts to move blood through their bodies and either an open or closed circulatory system

Circulation Open – blood partially contained in vessels 29-2 Form and Function in Invertebrates Circulation Open – blood partially contained in vessels Closed – blood forced through vessels 41

Circulation Open Circulatory Systems 29-2 Form and Function in Invertebrates Circulation Open Circulatory Systems   In an open circulatory system, blood is only partially contained within a system of blood vessels. One or more hearts or heartlike organs pump blood through blood vessels into a system of sinuses, or spongy cavities. The blood makes its way back to the heart.

29-2 Form and Function in Invertebrates Circulation Open circulatory systems are characteristic of arthropods and most mollusks. Most complex animals have one or more hearts to move fluid through their bodies in either an open or a closed circulatory system. An insect has an open circulatory system in which blood leaves blood vessels and then moves through sinuses, or body cavities.

Circulation Closed Circulatory Systems 29-2 Form and Function in Invertebrates Circulation Closed Circulatory Systems In a closed circulatory system, a heart or heartlike organ forces blood through vessels that extend throughout the body. Materials reach body tissues by diffusing across the walls of the blood vessels. Closed circulatory systems are characteristic of larger, more active animals.

29-2 Form and Function in Invertebrates Circulation Among the invertebrates, closed circulatory systems are found in annelids and some mollusks. Heartlike structure Small vessels in tissue Most complex animals have one or more hearts to move fluid through their bodies in either an open or a closed circulatory system. An annelid has a closed circulatory system in which blood stays in blood vessels as it moves through the body. Blood vessels Annelid: Closed Circulatory System Heartlike structures

29-2 Form and Function in Invertebrates Excretion Most animals have an excretory system that rids the body of metabolic wastes while controlling the amount of water in the tissues. In aquatic invertebrates, ammonia diffuses from their body tissues into the surrounding water.

Excretion Aquatic invertebrates: 29-2 Form and Function in Invertebrates Excretion Aquatic invertebrates: Diffusion: aquatic mollusks, sponges, and jelly fish Mollusk examples Flame cells: flatworms 47

Excretion Terrestrial Invertebrates Convert ammonia to urea 29-2 Form and Function in Invertebrates Excretion Terrestrial Invertebrates Convert ammonia to urea to conserve water Nephridia: Terrestrial mollusks and earthworms Malpighian tubules: insects and spiders 48

29-2 Form and Function in Invertebrates Excretion Flatworms use a network of flame cells to eliminate excess water. Flame Cells Excretory tubules Flame Cell Most animals dispose of wastes through excretory systems. Excretory systems also control an organism’s water levels. Flatworms excrete ammonia directly into the water and use flame cells to remove excess water. Excretory tubule Flatworm

29-2 Form and Function in Invertebrates Excretion In annelids and mollusks, urine forms in tubelike structures called nephridia. Nephrostome Excretory pore Most animals dispose of wastes through excretory systems. Excretory systems also control an organism’s water levels. Annelids use nephridia to convert ammonia into urea and to concentrate it in urine. Annelid Nephridia

29-2 Form and Function in Invertebrates Excretion Fluid enters the nephridia through openings called nephrostomes. Urine leaves the body through excretory pores. Urine is highly concentrated, so little water is lost.

29-2 Form and Function in Invertebrates Some insects and arachnids have Malpighian tubules, saclike organs that convert ammonia into uric acid. Excretion Digestive tract Most animals dispose of wastes through excretory systems. Excretory systems also control an organism’s water levels. Some arthropods have Malpighian tubules, which convert ammonia into uric acid. Uric acid is eliminated from the body in a paste. Malpighian tubules Arthropod

29-2 Form and Function in Invertebrates Excretion Uric acid and digestive wastes combine to form a thick paste that leaves the body through the rectum. The paste helps to reduce water loss.

29-2 Form and Function in Invertebrates Response Invertebrates show three trends in the evolution of the nervous system: centralization, cephalization, and specialization.

Response Nerve Nets: individual nerve cells in a net-like formation. 29-2 Form and Function in Invertebrates Nerve Nets: individual nerve cells in a net-like formation. Ganglia: Centralized nerve cells connected to the nerve net. Brain: Highly organized ganglia connected to nerve net. Specialization: when cells have a special job (ex: eyespots, eyes, chemical receptors, etc.) 55

Response Centralization and Cephalization 29-2 Form and Function in Invertebrates Response Centralization and Cephalization Cephalization is the concentration of nerve tissue and organs in one end of the body.

Response Specialization 29-2 Form and Function in Invertebrates Response Specialization The more complex an animal’s nervous system is, the more developed its sense organs tend to be. Complex animals may have a variety of specialized sense organs that detect light, sound, chemicals, movement, and electricity.

29-2 Form and Function in Invertebrates Response Cnidarians have nerve nets which consist of individual nerve cells that form a netlike arrangement throughout the animal’s body. Nerve cells Invertebrate nervous systems have different degrees of centralization, cephalization, and specialization. Cnidarians have a simple nerve net. Cnidarian

29-2 Form and Function in Invertebrates Response In flatworms and roundworms, the nerve cells are more centralized. There are a few clumps of nerve tissue, or ganglia, in the head. Ganglia Invertebrate nervous systems have different degrees of centralization, cephalization, and specialization. Flatworms, whose nervous systems are more centralized, have small ganglia in their heads. Flatworm

Response 29-2 Form and Function in Invertebrates Brain In cephalopod mollusks and arthropods, ganglia are organized into a brain. Ganglia Arthropod Brain Invertebrate nervous systems have different degrees of centralization, cephalization, and specialization. Arthropods and cephalopod mollusks have a centralized brain and specialized sensory organs. Mollusk

29-2 Form and Function in Invertebrates Movement and Support Most animals use muscles to move, breathe, pump blood, and perform other life functions. In most animals, muscles work together with some sort of skeletal system that provides firm support.

29-2 Form and Function in Invertebrates Movement and Support Hydrostatic skeleton: muscles surround a fluid-filled body cavity. Exoskeleton: Arthropods: Hard body covering made of chitin. Endoskeleton: Echinoderms: internal structural support. Hydrostatic: as the muscle contracts it pushed the fluid in another direction causing change in shape. 62

Movement and Support Hydrostatic Skeleton 29-2 Form and Function in Invertebrates Movement and Support Hydrostatic Skeleton Circular muscles contracted Water The three main types of invertebrate skeletons are hydrostatic skeletons, exoskeletons, and endoskeletons. In animals with hydrostatic skeletons, muscles contract against a fluid-filled body cavity. Longitudinal muscles contracted Water

Movement and Support Exoskeleton 29-2 Form and Function in Invertebrates Movement and Support Exoskeleton Flexed joint The three main types of invertebrate skeletons are hydrostatic skeletons, exoskeletons, and endoskeletons. In animals with hydrostatic skeletons, muscles contract against a fluid-filled body cavity. In animals with exoskeletons, the muscles pull against the insides of the exoskeleton. Extended joint

Movement and Support Endoskeleton 29-2 Form and Function in Invertebrates Movement and Support Endoskeleton The three main types of invertebrate skeletons are hydrostatic skeletons, exoskeletons, and endoskeletons. Echinoderms and some sponges have endoskeletons. Photo Credit: ©Lawrence Naylor/Photo Researchers, Inc. Skeletal plates Tube foot

Sexual & Asexual Reproduction 29-2 Form and Function in Invertebrates Sexual & Asexual Reproduction Sexual reproduction maintains genetic diversity in a population. Asexual reproduction allows animals to reproduce rapidly and take advantage of favorable conditions in the environment.

Sexual & Asexual Reproduction 29-2 Form and Function in Invertebrates Sexual & Asexual Reproduction Sexual reproduction is the production of offspring from the fusion of gametes. Male and female gametes join to create a zygote. The zygote grows through mitosis and develops into a multicellular animal.

Sexual & Asexual Reproduction 29-2 Form and Function in Invertebrates Sexual & Asexual Reproduction In most animals, each individual is a single sex. (male of female) The individual produces either sperm or eggs. Some animals are hermaphrodites—individuals that produce both sperm and eggs.

Sexual & Asexual Reproduction 29-2 Form and Function in Invertebrates Sexual & Asexual Reproduction In external fertilization, eggs are fertilized outside the female’s body. In internal fertilization, eggs are fertilized inside the female’s body.

Sexual & Asexual Reproduction 29-2 Form and Function in Invertebrates Sexual & Asexual Reproduction The offspring of asexual reproduction grow into multicellular organisms by mitosis of diploid cells. Some animals reproduce asexually through budding or by dividing in two.

29-2 Form and Function in Invertebrates Reproduction Most invertebrate reproduce sexually to increase genetic diversity. BUT….in certain conditions they will reproduce asexually in order to ensure continuation of species. 71