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Unit 1 Taxonomy Protozoa Early Embryonic Development Simple Metazoans

 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

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

 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

 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

 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

 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

 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=CD6v pheUoPE

 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

 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

Cladogram #1

moss conifer

fern

Chloro- Angiophyte sperm

multicellular

x

x

x

o

x

photosynthetic produces seeds

x

x

x

x

x

o

x

o

o

x

vascular

o

x

x

o

x

flowering

o

o

o

o

x

Cladogram #2 Bacteria Archaea Protozoa Animals DNA

Plants

Algae

Fungi

x

x

x

x

x

x

x

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

Autotrophic

Osteichthyes

Aves

Mammalia

Reptilia

Amphibia

Urochordata

Chondrichthyes

Cladogram #3 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

 Eukaryotic  Multicellular  Heterotrophic  No

cell wall  No Chloroplasts

 6.

Compare and contrast protozoans with animals  7. Describe means of locomotion employed by protozoans  8. Categorize major taxonomic groups of protozoans

 Animal-like

protists. Unicellular, but:

• Heterotrophic • Lack cell walls (usually) • Motile (usually)  http://www.youtube.com/watch?v=-

zsdYOgTbOk&feature=related

 Cilia  Relatively

short and densely distributed over the surface of the cell

 Flagellae  Longer

and

less numerous than cilia, but practically identical in internal structure

 Internal

structure consists largely of bundles of microtubules in a “9+2” arrangement  9 pairs in a circular arrangement with 2 in the middle

 http://www.youtube.com/watch?v=QGA

m6hMysTA

 Pseudopodia  Literally “false

feet”  Extensions of the cytoplasm used not only for movement but also for feeding

 http://www.youtube.com/watch?v=pvOz

4V699gk  http://www.youtube.com/watch?v=KeQ1 c6_Md1Q  http://www.youtube.com/watch?v=TOPM aNvGTvc  http://www.youtube.com/watch?v=d_Bk g8euB5Y

 Non-motile  All

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

 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

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, 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

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

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

 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”

 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

 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”

 Note

that there are 2 different patterns of cleavage, Radial and Spiral  Spiral cleavage results in greater early differentiation of cells

 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

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 

 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

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 

ASCONOID

SYCONOID

LEUCONOID

 The

simplest canal system  Choanocytes line the spongeocoel

 The

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

 Incurrent

canals direct water into specialized chambers lined with choanocytes  Excurrent canals direct water to the osculum to be expelled

 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