Chapter 7 Animal Classification, Phylogeny, and Organization Opener Chapter 7

July 11, 2018 | Author: Anonymous | Category: N/A
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Opener Chapter 7

Chapter 7 Animal Classification, Phylogeny, and Organization

Common names • Crawdads, crayfish, or crawfish? • English sparrow, barn sparrow, or a house sparrow?

Problem with common names • Vary from region to region • Common names often does not specify particular species

Binomial system of Nomenclature brings order to a chaotic world of common names • Universal • Clearly indicates the level of classification • No two kinds of animals have the same binomial name

• Every animal has one correct name International

Code of Zoological Nomenclature

• Genus begins with a Capital letter

• Entire name italicized or underlined

• Homo sapien or H. sapien

The three domains • Arhaea- prokaryotic microbes live in extreme environments, inhabit anaerobic environments • Reflect the conditions of early life • Archaea the most primitive life form • Archaea give rise to two other domains – Eubacteria- true bacteria and are prokaryotic microorganisms – Eukarya- include all eukaryotic organisms, diverged more recently thus more closely related to archae (protists, fungi, plants and animals)

Figure 7.2 (b)

Kingdom of Life 1969 R. Whittaker- five kingdom classification System of classification that distinguished b/w kingdoms according to • cellular organization • mode of nutrition

Figure 7.2 (a)

Monera- bacteria and cyanobacteria are prokaryotic

• Protista- single or colonies of eukaryotic cells (Ameoba, Paramecium)

• Plantae- eukaryotic, multicellular, and photosynthtic. Have cell wall, and usually nonmotile

• Fungi-eukaryotic and multicellular. Have cell wall and nonmotile. Mode of nutrition distiguishes fungi from plantfungi digest extracellularly and absorb the breakdown products

• Animalia- eukaryotic and multicellular, usually feed by ingesting other organisms, cell lack cell walls, and usually motile

Text devoted to animals • Except for Chapter 8 Animal like protists (Amoeba and Paramecium) • The inclusion of protozoa is part of a tradition • Once considered a phylum (Protozoa) in the animal kingdom

Pattern of Organization • Asymmetry – i.e. ameoba

• Symmetry – Radial symmetry- tube coral pulp – Bilateral symmetry- insects

Figure 7.7 Asymmetry red encrusting sponge

Figure 7.8

Radial symmetry tube coral pulp

Part 2

Bilateral animals

• Bilateral symmetry = important evolutionary advancement – Important for active, directed movement • Anterior, posterior ends – One side of body kept up (dorsal) vs. down (ventral)

Directed movement evolved with anterior sense organs cephalization Cephalization – specialization of sense organs in head end of animals

Bilateral Symmetry • Divided along sagittal plane into two mirror images – sagittal= divides bilateral organisms into right and left halves

• • • •

Anterior= head end Posterior= tail end Dorsal= back side Ventral= belly side

• Symmetry, fig. 7.9 – Median= sagittal

Other Patterns of Organization may reflect evolutionary trends • Unicellular (cytoplasmic)- organisms consist of single cells or cellular aggregates, – provide functions of locomotion, food acquisition, digestion, water and ion regulation, sensory perception and reproduction in a single cell.

– Cellular aggregates consist of loose association, cells that exhibit little interdependence, cooperation, or coordination of function – Some cells may be specialized for reproduction, nutritive or structural function

• The analogy of a clock – Can be used to place major events in the Earth’s history in the context of the geological record Cenozoic Humans

~500 million years ago Land plants Origin of solar system and Earth


Algea fossils

e 26.10


1 Proterozoic Eon

Archaean Eon

Billions of years ago 2


Multicellular eukaryotes


Single-celled eukaryotes Atmospheric oxygen

• Larger organisms do not appear in the fossil record – Until several hundred million years later

• Chinese paleontologists recently described 570million-year-old fossils – That are probably animal embryos

(a) Two-cell stage

150 m

(b) Later stage 200 m

The Colonial Connection

• The first multicellular organisms were colonies – Collections of autonomously replicating cells

10 m

May Lead to Cell Specialization

• Organisms can have more than one tissue layer – Diploblastic- two layers

What about Tripoblastic – three layers?

• Diploblastic Organization- Two tissue layers – Cells are organized into tissues in most animal phyla – Body parts are organized into layers derived from two embryonic tissue layers. – Ectoderm- Gr. ektos, outside + derm, skin gives rise to the epidermis the outer layer of the body wall – Endoderm- Gr. Endo, within, gives rise to the gastrodermis that lines the gut

Mesoglea- between the ecto and endo and may or may not contain cells – Derived from ecto and/or endo – Cells form middle layer (mesenchyme)

– Layers are functionally inderdependent, yet cooperate showing tissue level organization i.e. feeding movements of Hydra or swimming movements of a jellyfish

Figure 7.10

The Triploblastic (treis, three +blaste, sprout) • • • •

Animals described in chapters 10-22 Tissues derived from three embryological layers Ectoderm- outer layer Endoderm- lines the gut

• Mesoderm- meso, middle, Third layer between Ecto and Endo – Give rise to supportive cells

Figure 7.11

Diploblastic Triploblastic

Diploblastic or Triploblastic?

Triploblastic animal

• Most have an organ system level of organization • Usually bilaterally symmetrical or evolved from bilateral ancestors • Organized into several groups based on the presence or absence of body cavity and for those that posses one, the kind of body cavity present. • Body cavity- fluid filled space in which the internal organs can be suspended and separated from the body wall

Body cavities are advantageous 1. Provide more room for organ development 2. Provide more surface area for diffusion of gases, nutrients, and waste into and out of organs 3. Provide area for storage 4. Often act as hydrostatic skeletons (supportive yet flexible) 5. Provide a vehicle for eliminating wastes and reproductive products from the body 6. Facilitate increase in body size

What does acoelomate mean? No coelom

Acoelomate a, without+ kilos, hollow • Mesoderm relatively solid mass • No cavity formed between ecto and endo • These cells within mesoderm often called parenchymal cells • Parenchymal cells not speciallized for a particular fnc.

What’s a coelom?

• coelom= – true body cavity – Fluid-filled – lined by mesoderm-derived epithelium


• Acoelomates lack a true body cavity – Solid body – no cavity b/w the digestive tract and outer body wall

Do these questions now…

• Think about aceolomate bilateral animals: – To what domain do they belong – “ ” kingdom ” ” ” – What phyla include these organisms

• What is bilateral symmetry, and why was it an important evolutionary advantage


Acoelomate Bilateral Animals • Consist of phyla: – Phylum Platyhelminthes – Phylum Nemertea – Others…

Acoelomate Bilateral Animals


Simplest organisms to have bilateral symmetry




Lack a coelom


Organ-system level of organization




Elongated, without appendages

Reproductive and osmoregulatory systems

Acoelomate Bilateral Animals


Simplest organisms to have bilateral symmetry




Lack a coelom


Organ-system level of organization




Elongated, without appendages

Reproductive and osmoregulatory systems

Triploblastic Pseudocoelomate pseudes, false • Body cavity not entirely lined by mesoderm • No muscle or connective tissue associated with gut • No mesodermal

The Triploblastic Coelomate Pattern • Coelom is a body cavity completely surrounded by mesoderm • Peritoneum- mesodermal sheet that lines the inner body wall and serosa (outer covering of visceral organs) • Having mesodermally derived tissue (muscle, connective tissue) enhances the function of all internal body systems.

Figure 7.12

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