Chapter 32 Introduction to Animal Diversity

Transcription

1 Chapter 32 Introduction to Animal Diversity

2 Review: Biology 101 There are 3 domains: They are Archaea Bacteria Protista! Eukarya

3 Endosymbiosis (proposed by Lynn Margulis) is a relationship between two species in which one organism lives inside the cell or cells of the other organism (the host) This is the root of the diversity of life.

4 Mitochondria and plastids are derived from prokaryotes that were engulfed by the ancestors of early eukaryotic cells Mitochondria evolved once by endosymbiosis of an alpha proteobacterium The ancestral host cell may have been an archaean or a protoeukaryote, from a lineage related to, but diverged from archaeal ancestors

5 What makes a Kingdom? A Kingdom is a division of life, right under Domain. Boundless. The Levels of Classification. Boundless Biology. Boundless, 03 Jul Retrieved 12 Dec from ess-biology-textbook/phylogenies-and-the-history-of-life- 20/organizing-life-on-earth-133/the-levels-of-classification //

6 Welcome to Your Kingdom The animal kingdom extends far beyond humans and other animals we may encounter 1.3 million living species of animals have been identified Fig. 32-1

7 Animal characteristics Animals are heterotrophs that ingest their food

8 What makes an Animal? Animals are multicellular eukaryotes Heterotrophs that digest internally Their cells lack cell walls Their bodies are held together by structural proteins such as collagen Nervous tissue and muscle tissue are unique to animals

9 Reproduction and Development Most animals reproduce sexually, with the diploid stage usually dominating the life cycle After a sperm fertilizes an egg, the zygote undergoes rapid cell division called cleavage Cleavage leads to formation of a blastula The blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissues

10 The Earth is very old The Earth is about 4.5 billion (4,500,000,000) years old. The geological time scale divides up this vast time interval.

11 The history of animals spans more than half a billion years The animal kingdom includes a great diversity of living species and an even greater diversity of extinct ones The common ancestor of living animals may have lived between 675 and 875 million years ago This ancestor may have resembled modern choanoflagellates, protists that are the closest living relatives of animals

12 The oldest fossils (bacteria) are between 3 billion and 3.5 billion years old. More complex animals appeared in the oceans about 565 million years ago, and became much more common about 542 million years ago. This is the start of a division of geological time called the Phanerozoic Eon. Phanerozoic means "visible life", and is the time in which fossils are abundant.

13 Neoproterozoic Era (1 Billion 524 Million Years Ago) Early members of the animal fossil record include the Ediacaran biota, (pre-cambrian) which dates from 565 to 550 million years ago All life was soft-bodied Mawsonites spriggi Spriggina floundersi

14 Paleozoic Era ( Million Years Ago) The Cambrian explosion (535 to 525 million years ago) marks the earliest fossil appearance of many major groups of living animals Several hypotheses regarding the explosion 1. New predator-prey relationships 2. A rise in atmospheric oxygen 3. The evolution of the Hox gene complex

15 Fig. 32-5

16 Animal diversity continued to increase through the Paleozoic, but was punctuated by mass extinctions Animals began to make an impact on land by 460 million years ago Vertebrates made the transition to land around 360 million years ago

17 Mesozoic Era ( Million Years Ago) Coral reefs emerged, becoming important marine ecological niches for other organisms During the Mesozoic era, dinosaurs were the dominant terrestrial vertebrates The first mammals emerged

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19 Cenozoic Era (65.5 Million Years Ago to the Present) The beginning of the Cenozoic era followed mass extinctions of both terrestrial and marine animals These extinctions included the large, nonflying dinosaurs and the marine reptiles Modern mammal orders and insects diversified during the Cenozoic

20 Animals can be characterized by body plans A body plan is a set of morphological and developmental traits we will classify animals by: 1. Symmetry 2. Tissues 3. Type of body Cavity 4. Fate of the blastopore

21 All animals, and only animals, have Hox (Homeobox) genes Hox regulates the development of body form Lay out the basic body form of all animals it doesn t matter if it s a mouse s head or a fly s head that is being built, the same gene directs the process Jellyfish have only two Hox genes, bilateria have at least seven.

22 Metamorphosis - Some animals change body plans during their life-cycle Many animals have at least one larval stage A larva is sexually immature and morphologically distinct from the adult; it eventually undergoes metamorphosis

23 1. Symmetry Animals can be categorized according to the symmetry of their bodies, or lack of it Sponges are asymmetrical they have asymmetry

24 1. Symmetry Animals can be categorized according to the symmetry of their bodies, or lack of it Some animals have radial symmetry Fig. Copyright Pearson Education, Inc., publishing as Pearson Benjamin Cummings (a) Radial symmetry

25 1. Symmetry (b) Bilateral symmetry Bilaterally symmetrical animals have: A dorsal (top) side and a ventral (bottom) side A right and left side Anterior (head) and posterior (tail) ends Cephalization, the development of a head Fig. Copyright Pearson Education, Inc., publishing as Pearson Benjamin Cummings

26 2. Tissues Tissues are collections of specialized cells isolated from other tissues by membranous layers During development germ layers give rise to the tissues and organs of the animal embryo

27 2. Tissues Ectoderm is the germ layer covering the embryo s surface Endoderm is the innermost germ layer and lines the developing digestive tube. Diploblastic animals have ectoderm and endoderm Triploblastic animals also have an intervening mesoderm layer; these include all bilaterians

28 3. Body Cavities Most triploblastic animals possess a body cavity A true body cavity is called a coelom and is derived from mesoderm

29 3. Body Cavities Animals that are Diploblastic (like jellyfish) or do not form a blastula (like sponges) have no body cavity. We say that they have No Coelom

30 3. Body Cavities Triploblastic animals that lack a body cavity are called acoelomates Body covering (from ectoderm) Tissuefilled region (from mesoderm) Wall of digestive cavity (from endoderm) (c) Acoelomate

31 3. Body Cavities A pseudocoelom is a body cavity derived from the mesoderm and endoderm Triploblastic animals that possess a pseudocoelom are called pseudocoelomates Body covering (from ectoderm) Pseudocoelom Digestive tract (from endoderm) Muscle layer (from mesoderm) (b) Pseudocoelomate

32 3. Body Cavities Coelomates are animals that possess a true coelom Coelom Body covering (from ectoderm) Digestive tract (from endoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) (a) Coelomate Fig. 32-8a

33 4. Protostome and Deuterostome Development Based on early development, many animals can be categorized as having protostome development or deuterostome development Blastocoel Cleavage Cleavage Blastula Endoderm Ectoderm Zygote Eight-cell stage Archenteron Gastrulation Gastrula Blastocoel Blastopore Cross section of blastula

34 4. Protostome and Deuterostome Development The blastopore forms during gastrulation Protostome:blastopore becomes the mouth Deuterostome: the blastopore becomes the anus Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Anus Digestive tube Mouth (c) Fate of the blastopore Key Ectoderm Mesoderm Endoderm Mouth Anus Mouth develops from blastopore. Anus develops from blastopore. Fig. 32-9c

35 4. Protostome and Deuterostome Development Protostome: the splitting of solid masses of mesoderm forms the coelom Deuterostome: the mesoderm buds from the wall of the archenteron to form the coelom Protostome development (examples: molluscs, annelids) Deuterostome development (examples: echinoderms, chordates) Coelom Archenteron Coelom (b) Coelom formation Key Ectoderm Mesoderm Endoderm Mesoderm Blastopore Blastopore Mesoderm Solid masses of mesoderm split and form coelom. Folds of archenteron form coelom. Fig. 32-9b

36 Porifera Figure ANCESTRAL PROTIST Metazoa 770 million years ago Eumetazoa 680 million years ago Bilateria 670 million years ago Deuterostomia Lophotrochozoa Ecdysozoa Ctenophora Cnidaria Acoela Hemichordata Echinodermata Chordata Platyhelminthes Rotifera Ectoprocta Brachiopoda Mollusca Annelida Nematoda Arthropoda

37 Five important points about the relationships among living animals are reflected in their phylogeny 1. All animals share a common ancestor 2. Sponges are basal animals 3. True animals Eumetazoa is a clade of animals with true tissues 4. Most animal phyla belong to the clade Bilateria 5. Most animals (95%) are invertebrates, animals that lack a backbone, only some Chordata, are classified as vertebrates.

38 You should now be able to: 1. List the characteristics define animals 2. Summarize key events of the Paleozoic, Mesozoic, and Cenozoic eras 3. Distinguish between the following pairs or sets of terms: radial and bilateral symmetry; grade and clade of animal taxa; diploblastic and triploblastic; spiral and radial cleavage; determinate and indeterminate cleavage; acoelomate, pseudocoelomate, and coelomate grades

39 4. Compare the developmental differences between protostomes and deuterostomes 5. Compare the alternate relationships of annelids and arthropods presented by two different proposed phylogenetic trees 6. Distinguish between ecdysozoans and lophotrochozoans