ZoologyUnit 1

TaxonomyProtozoa

Early Embryonic DevelopmentSimple Metazoans

Chapter 10 - Taxonomy 1. List the hierarchy of taxonomic ranks in

the modern classification system 2. Compare & contrast concepts of

species identification 3. Explain how taxonomic characters are

used to infer evolutionary relationships 4. Define “clade”. Use shared and

derived characters to construct cladograms 5. Identify characteristics that define the

Animal Kingdom

Taxonomic Ranks Taxonomic groupings are of human

design, and are organized in a way to simplify our thinking about living organisms

Early taxonomic systems recognized two Kingdoms, Plant and Animal

As more varied organisms have been discovered, many do not neatly fit into either the Plant or Animal Kingdom

Conflicts in Early Taxonomy

Fungi have cell walls and are sessile, but cannot make their own food

Many single celled organisms are capable of photosynthesis, but have well developed mechanisms for locomotion

Cyanobacteria (formerly known as Cyanophyta) are photosynthetic, but lack organelles and a true nucleus

Modern Taxonomy Taxonomic systems expanded from the

early 2 kingdom approach to the recognition of 5 kingdoms: Monera (the bacteria), Protista, Fungi, Plantae, and Animalia

Improvements in analytical techniques have uncovered significant differences in bacteria resulting in the recognition of 2 distinct types, Archaebacteria and Eubacteria

A new level at the top: Domain

Modern trends in taxonomy emphasize ancestral relationships over convenience. The addition of Domain above the Kingdom level allows grouping of related Kingdoms. There are 3 recognized Domains:• Archaea – Includes the Kingdom Archaebacteria• Eubacteria – The “true Bacteria”• Eukarya – Eukaryotes:

Includes Kingdom Protista, Fungi, Plantae and Animalia

Species There are different approaches to the

recognition of species. Each approach has advantages and disadvantages• Morphological Species Concept

Based on body form characteristics• Biological Species Concept

Based on the ability to interbreed• Evolutionary and Phylogenetic Species

Concepts Based on ancestral/evolutionary relationships

Biological Species Concept Based on the ability to interbreed Some closely related species can

interbreed, but their offspring are sterile (example: lion x tiger = liger)

http://www.youtube.com/watch?v=CD6vpheUoPE

Reflecting Ancestry in Taxonomy

Accurate interpretations of evolutionary relationships require a variety of evidence. The difficulty lies in determining which similarities are superficial and which reflect common ancestry• “Homology” reflects common ancestry• “Analogous” traits are evolved

independently in separate lineages

The Cladistic Approach Modern taxonomy is moving towards

greater emphasis on common ancestry Cladistics is based on identifying an

ancestral characteristic present in a lineage

Progressively smaller groupings are formed as the result of “derived” characteristics

A “clade” includes all descendants of a particular ancestral lineage

Sample Cladogram

Create a Cladogram Cladogram #1 moss conifer fern

Chloro-phyte

Angio-sperm

multicellular x x x o x

photosynthetic x x x x xproduces seeds o x o o x

vascular o x x o x

flowering o o o o x

Cladogram Sample #2

Cladogram #2 Bacteria Archaea Protozoa Animals Plants Algae Fungi

DNA x x x x x x x

Autotrophic some some o o x x o

Cell Wall x o o o x x x

Multicellular o o o x x o some

Peptidoglycan x o o o o o o

Nucleus o o x x x x x

Cladogram Sample #3

Cladogram #3Chondrichthyes

Urochordata

Amphibia Reptilia

Mammalia Aves

Osteichthyes

paired limbs o o x x x x o

feathers o o o o o x o

amniote egg o o o x x x o

mammary glands o o o o x o o

vertebrae x o x x x x x

notocord x x x x x x x

bony skeleton o o x x x x x

Kingdom Animalia Eukaryotic Multicellular Heterotrophic No cell wall No

Chloroplasts

Chapter 11 - Protozoa 6. Compare and contrast

protozoans with animals 7. Describe means of locomotion

employed by protozoans 8. Categorize major taxonomic

groups of protozoans

Protozoans = “first animals”

Animal-like protists. Unicellular, but:• Heterotrophic• Lack cell walls (usually)• Motile (usually)

http://www.youtube.com/watch?v=-zsdYOgTbOk&feature=related

Modes of Protozoan Locomotion

Cilia Relatively

short and densely distributed over the surface of the cell

Modes of Protozoan Locomotion

Flagellae Longer and

less numerous than cilia, but practically identical in internal structure

Structure of Cilia & Flagellae

Internal structure consists largely of bundles of microtubules in a “9+2” arrangement

9 pairs in a circular arrangement with 2 in the middle

Cilia and Flagellae http://www.youtube.com/watch?v=Q

GAm6hMysTA

Modes of Protozoan Locomotion

Pseudopodia Literally “false

feet” Extensions of

the cytoplasm used not only for movement but also for feeding

Feeding and Movement of Amoebae

http://www.youtube.com/watch?v=pvOz4V699gk

http://www.youtube.com/watch?v=KeQ1c6_Md1Q

http://www.youtube.com/watch?v=TOPMaNvGTvc

http://www.youtube.com/watch?v=d_Bkg8euB5Y

Modes of Protozoan Locomotion

Non-motile All of these

types are parasitic and rely on a “vector” for movement to a new host

Traditional Protozoan Taxonomy

Since motility is a trait generally associated with Animals, categorizing the protozoa by their locomotion was a logical approach:

Flagellates – use flagellae Ciliates – use cilia Sarcodines – use pseudopodia Sporozoans – are nonmotile

Chapter 12 – Simple Metazoans 9. Discuss the colonial flagellate hypothesis of

metazoan origin 10. Identify distinguishing characteristics of the

phylum mesozoa 11. Identify distinguishing characteristics of the

phylum placozoa 12. Identify distinguishing characteristics of the

phylum porifera 13. Discuss the fundamental anatomy of sponges 14. Relate variations in sponge canal systems to

feeding efficiency 15. Categorize the classes of sponges

Metazoans Metazoans, in contrast with

Protozoans, are truly multicellular (with some differentiation of tissues)

The most “primitive” of the metazoa are barely more than colonies of cells, but have some cells specialized for feeding, or reproduction, or locomotion

Protozoan Ancestor to Animalia 2 hypotheses have been advanced as to

the protozoan ancestor to the animals:• Amoeboid ancestor• Flagellate ancestor

Cells resembling each of these protozoan forms exist in some form within the Animal kingdom

The more accepted hypothesis is the Flagellate ancestor hypothesis

Flagellate Ancestor Hypothesis

Cells called “Choanocytes” in sponges are identical in form and behavior to Choanoflagellate protists, which may be free living or colonial

Multicellularity Multicellular organisms differ from

colonial organisms due to the specialization of cells and the division of labor that results.

Groups of cells that are structurally and functionally specialized are “tissues”

Tissues that combine together for related functions are “organs”

Organs that perform a broad coordinated function form a “system”

Differentiation & Development All animals share a common pattern of

embryonic development (suggesting a common ancestry)

Much of the phylogeny of Kingdom Animalia can be traced back to variations in early embryonic development

Animal phyla generally considered “primitive” only go through a few stages of development, while the more “complex” phyla go through additional stages

Early Embryonic Development

The zygote divides in two (“cleavage”), then 4, then 8, forming a raspberry shaped “morula”

Cleavage continues forming a hollow ball of cells called a “blastula”

Cleavage Patterns and Differentiation

Note that there are 2 different patterns of cleavage, Radial and Spiral

Spiral cleavage results in greater early differentiation of cells

Gastrulation The blastula caves

in on one end, forming an inner layer (endoderm) and an outer layer (ectoderm)

The resulting space (“Archenteron”) will form the digestive cavity

Phylum Mesozoa Mesozoa are basically an

elongated Morula – They never reach the Blastula stage

Mesozoans are at the “cellular level” of organization. No true tissues exist

The inner layer of cells are specialized for reproduction

All known forms are parasitic

Phylum Placozoa The body form of

placozoans is a flattened Blastula

Placozoa are also at the cellular level of organization

The “oral” surface is specialized for feeding and locomotion

Phylum Porifera – The Sponges

Phylum Porifera The name Porifera is

derived from many pores (ostia) that allow water to flow through the channels in the body wall, allowing the sponge to filter feed

The flow of water is driven by flagellated “choanocytes” lining the channels

Sponge Anatomy

Canal System Variations

SYCONOIDASCONOID LEUCONOID

Asconoid Sponges The simplest canal system Choanocytes line the spongeocoel

Syconoid Sponges The pouching

of the spongeocoel into radial canals increases the surface area of contact between choanocytes and water flow

Leuconoid Sponges

Incurrent canals direct water into specialized chambers lined with choanocytes

Excurrent canals direct water to the osculum to be expelled

Spongin and Spicules

Sponge Phylogeny Phylum Porifera is divided into 3 classes Class Calcarea

• Calcium carbonate spicules • All 3 canal system types represented

Class Hexactinellidae• 6 rayed, siliceous spicules• Syconoid or Leuconoid canal systems

Class Demospongiae• Siliceous spicules (not 6 rayed), spongin• Leuconoid canal systems