Ch 26 Animal Evolution and Diversity

Ch 26.1 Invertebrate Evolution and Diversity

Objectives:
Explain what fossil evidence indicates about the timing of the evolution of the first animals
Interpret the cladogram of invertebrates

Ch 26.1 Invertebrate Evolution and Diversity
Origins of Invertebrates

Traces of Early Animals
Multicellular life – 600 MYA – fossil record
Thought to be tiny, soft-bodied so few fossilized examples exist
Fossils of eggs and embryos have been discovered as well as “trace” fossils
Tracks and burrows made by animals whose remains were not fossilized
Ediacaran Fauna – Australia; dated before the Cambrian Period; seem to be related to jellyfishes and worms; 565 – 544 MYA

The Cambrian Explosion

• Complex body plans
  
  

• Specialized cells, tissues, and organs
  
  

• Body symmetry, segmentation, front and back ends, appendage
  
  

• Early arthropods
  
  

Nonchordate Invertebrates
A. Cladogram (p. 754)
Presents evidence about relationships
Sequence of important events

Image 2:

B. Phyla include:

1. Porifera
   
   

2. Cnidaria
   
   

3. Arthropoda
   
   

4. Nematoda
   
   

5. Platyhelminthes
   
   

6. Annelida
   
   

7. Mollusca
   
   

8. Echinodermata
   
   

C. Features that we see include:

1. Body symmetry
   
   

2. Cephalization
   
   

3. Segmentation
   
   

4. Formation of a coelom
   
   

Ch 26.2 Chordate Evolution and Diversity

Objectives:
Describe the most ancient chordates
Interpret the cladogram of chordates

Ch 26.2 Chordate Evolution and Diversity

I. Origins of Chordates
A. The Earliest Chordates

1. Most likely relatives of echinoderms
   
   

2. Characteristics
   a. Paired muscles; cartilage; fins, feathery gills, skull with sense organs
   
   

B. Modern Chordates

1. Include:
   a. Nonvertebrate Chordates – lancelets, tunicates
   b. Fishes
   c. Amphibians
   d. Reptiles
   e. Birds
   f. Mammals
   
   

Early Chordate: Pikaia

Image 3:

Ch 26.2 Chordate Evolution and Diversity
Fishes

Jawless fishes – Class Agnatha
Characteristics
➀ Lack vertebrae
➁ Have notochords as adults
➂ Ex: lampreys, hagfish (slime eels)

Sharks and Their Relatives – Class Chondrichthyes
Characteristics
➀ Paired fins
➁ Cartilaginous skeletons
➂ Ex: sharks, rays, skates

Ch 26.2 Chordate Evolution and Diversity
Bony Fishes – Class Osteichthyes
➀ Identified by hard, bony, calcium-based skeletons
➁ Ray-finned fishes
➤ Paired fins, scales, gills
➤ Rays connect by a layer of skin to form fins
➤ Ex: eels, catfish, goldfish

Ch 26.2 Chordate Evolution and Diversity
Lobe-finned Fishes
➀ Characterized by fleshy fins supported by larger, more substantial bones
➁ Ex: lungfishes, coelacanth
➂ Thought to have evolved into tetrapods – a forerunner of the amphibians

All fishes are ectothermic – lays eggs externally; external fertilization; separate sexes

Ch 26.2 Chordate Evolution and Diversity
Amphibians – Class Amphibia
Means “double life”; live in water as larvae, on land as adults; lay eggs in water – external fertilization;
ectothermic; 3 chambered heart
Require water for reproduction; moist skin; lack scales and claws
Orders
① Anura – frogs and toads
② Caudata – salamanders
③ Gymnophiona – caecilians

Ch 26.2 Chordate Evolution and Diversity
Reptiles – Class Reptilia
🦎 Dry, scaly skin; well-developed lungs; strong limbs; shelled eggs that do not develop in water; 3 chambered heart (except alligators and crocodiles)
Ectothermic – internal fertilization;
Orders
① Squamata – lizards and snakes,
② Crocodilia – crocodiles, alligators
③ Testudinia – turtles and tortoises
④ Sphenodontia – tuatara

Ch 26.2 Chordate Evolution and Diversity
Birds – Class Aves
Endothermic; outer covering of feathers (modified scales?); strong, lightweight bones; 2 legs covered with scales; front limbs modified as wings; lay eggs;
internal fertilization
First birdlike fossil – Archaeopteryx – Jurassic Pd – 150 MYA

Ch 26.2 Chordate Evolution and Diversity
Mammals – Class Mammalia
5000 species
Mammary glands in females; hair; 4-chambered heart; endothermic.

3 major groups
a. Monotremes (egg-layers) – duck-billed platypus, spiny anteaters (Echidna)
b. Marsupials – bear live young which complete development in a pouch
c. Placentals – embryos develop within a womb

Chapter 26.3 Primate Evolution
What Is a Primate?
Characteristics
Relatively long fingers and toes with nails instead of claws
Arms that can rotate around shoulder joints
Strong clavicle
Binocular vision
Well-developed cerebrum

Chapter 26.3 Primate Evolution
Evolution of Primates
Lemurs and Lorises
Small, nocturnal primates; large eyes; long snouts
Ex: bush babies (Africa), lemurs (Madagascar), lorises (Asia)

Chapter 26.3 Primate Evolution
Tarsiers and Anthropoids
Characteristics
Broad faces, wide nostrils; humanlike primates
Ex: monkeys, great apes, humans

New World Monkeys
Found in Central and South America
Long flexible arms, prehensile tail “fifth hand”
Ex: squirrel monkeys, spider monkeys

Chapter 26.3 Primate Evolution
Hominine Evolution
Hominines – includes modern humans and species more closely related to humans than chimpanzees
Characteristics
Walking upright; skull, neck, spinal column, hip bones, leg bones aligned for bipedal movement
Opposable thumbs
Large brains
Ex: Australopithecus

Chapter 26.3 Primate Evolution
The Road to Modern Humans
Many variations of the genus Homo are thought to have existed

• Homo habilis
  
  

• H. ergaster
  
  

• H. rudolfensis
  
  

• H. neanderthalensis
  
  

• H. sapiens