Comparing Invertebrates Chapter 29 Invertebrate Evolution Chapter 29

Comparing Invertebrates Chapter 29

Invertebrate Evolution Chapter 29 -1

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

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

29 -1 Invertebrate Evolution The First Multicellular Animals l 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

29 -1 Invertebrate Evolution Invertebrate Phylogeny l 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

29 -1 Invertebrate Evolution Invertebrate Phylogeny l Invertebrate Evolutionary Relationships

29 -1 Invertebrate Evolution Invertebrate Phylogeny Roundworms Flatworms Cnidarians Sponges Unicellular ancestor

29 -1 Invertebrate Evolution Invertebrate Phylogeny

29 -1 Invertebrate Evolution Invertebrate Phylogeny

29 -1 Invertebrate Evolution Invertebrate Phylogeny l Invertebrate Evolutionary Relationships

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

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

29 -1 Invertebrate Evolutionary Trends l 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

29 -1 Invertebrate Evolutionary Trends l 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.

29 -1 Invertebrate Evolutionary Trends • Coelom Formation • Flatworms are acoelomates. This means they have no coelom, or body cavity, that forms between the germ layers. Ectoderm Mesoderm Digestive cavity Acoelomate Endoderm

29 -1 Invertebrate Evolutionary Trends l Pseudocoelomates have a body cavity lined partially with mesoderm. Pseudocoelom Digestive tract Pseudocoelomate

29 -1 Invertebrate Evolutionary Trends • Most complex animal phyla have a true coelom that is lined completely with tissue derived from mesoderm. Coelom Digestive tract Coelomate

29 -1 Invertebrate Evolutionary Trends

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

29 -1 Invertebrate Evolutionary Trends l l 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.

29 -1 Invertebrate Evolutionary Trends

29 -1 Invertebrate Evolutionary Trends

Invertebrate Form & Function Chapter 29 -2

The End

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

29 -2 Form and Function in Invertebrates Feeding and Digestion l 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 l l 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 l l l 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 l l 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.

29 -2 Form and Function in Invertebrates Feeding and Digestion Mouth/anus Gastrovascular cavity Digestive cavity Cnidarian Pharynx Mouth/anus Flatworm

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

29 -2 Form and Function in Invertebrates Intestine Feeding and Digestion Gizzard Crop Pharynx Mouth Annelid Anus Pharynx Crop Anus Arthropod Mouth Stomach and digestive glands Rectum Intestine

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

29 -2 Form and Function in Invertebrates Respiration l Aquatic invertebrates: § Require moist respiratory surfaces § Some through the pores of the skin § Some through gills (large feathery structure rich in blood vessels)

29 -2 Form and Function in Invertebrates Respiration • Aquatic Invertebrates • Gills are feathery structures that expose a large surface area to the water.

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

29 -2 Form and Function in Invertebrates Respiration • Terrestrial Invertebrates l Grasshoppers and other insects have spiracles and tracheal tubes.

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

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

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 l Open circulatory systems are characteristic of arthropods and most mollusks.

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 l Among the invertebrates, closed circulatory systems are found in annelids and some mollusks. Heartlike structure Small vessels in tissue Annelid: Closed Circulatory System Blood vessels 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.

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

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

29 -2 Form and Function in Invertebrates Excretion l Flatworms use a network of flame cells to eliminate excess water. Flame Cells Excretory tubules Flame Cell Flatworm Excretory tubule

29 -2 Form and Function in Invertebrates Excretion l In annelids and mollusks, urine forms in tubelike structures called nephridia. Nephrostome Excretory pore Annelid Nephridia

29 -2 Form and Function in Invertebrates Excretion l l l 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 l Some insects and arachnids have Malpighian tubules, saclike organs that convert ammonia into uric acid. Digestive tract Arthropod Excretion Malpighian tubules

29 -2 Form and Function in Invertebrates Excretion l l 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.

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

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.

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 l Cnidarians have nerve nets which consist of individual nerve cells that form a netlike arrangement throughout the animal’s body. Nerve cells Cnidarian

29 -2 Form and Function in Invertebrates Response l l In flatworms and roundworms, the nerve cells are more centralized. There a few clumps of nerve tissue, or ganglia, in the head. Ganglia Flatworm

29 -2 Form and Function in Invertebrates Response Brain l In cephalopod mollusks and arthropods, ganglia are organized into a brain. Ganglia Arthropod Brain Mollusk

29 -2 Form and Function in Invertebrates Movement and Support l l 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 l Hydrostatic skeleton: muscles surround a fluid-filled body cavity. l Exoskeleton: Arthropods: Hard body covering made of chitin. l Endoskeleton: Echinoderms: internal structural support.

29 -2 Form and Function in Invertebrates Movement and Support • Hydrostatic Circular muscles contracted Skeleton Water Longitudinal muscles contracted Water

29 -2 Form and Function in Invertebrates Movement and Support • Exoskeleton Flexed joint Extended joint

29 -2 Form and Function in Invertebrates Movement and Support • Endoskeleton Skeletal plates Tube foot

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

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

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

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

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

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