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Animal Diversity and Form &
Function
Announcements
- This weekend – Dr. Hannam will finalize PRS corrections and contact students with problems
- Quiz #1 – closed. Will be reopened for review and grades posted this weekend.
- Homework #2 will be posted over the weekend. An hypothesis for chordate evolution: key characteristics in evolution Notochord Vertebral Column Jaws Amniotic Egg Lungs Legs Which of the following is not a characteristic of ALL organisms in the phylum chordata at some point in their development cycle? (a) notochord (b) backbone (c) muscular, post anal tail (d) pharyngeal slits (e) dorsal,hollow nerve cord Which phylum is characterized by animals that have a
segmented body?
- A. Cnidaria
- B. Platyhelminthes
- C. Porifora
- D. Arthropoda
- E. Mollusca Incurrent siphon Excurrent siphon (^) Muscle segments Atrium Intestine Stomach Tail Dorsal, hollow nerve cord Pharynx with slits Notochord
- Tunicates most resemble chordates during their larval stage, which may last only a few minutes
Invertebrate Chordates
Adult Sea Squirt http://commons.wikimedia.org/wiki/File:Tunicate_komodo.jpg – N. Hobgood
Dorsal, hollow nerve cord Notochord Tentacle Segmental muscles Mouth Pharyngeal slits Atrium Digestive tract Atriopore Anus Tail 2 cm Lancelets are named for their bladelike shape They are marine suspension feeders that retain characteristics of the chordate body plan as adults
Invertebrate Chordates
An hypothesis for chordate evolution: key characteristics in evolution Notochord Vertebral Column Jaws Amniotic Egg Lungs Legs Craniates
Craniates: chordates with a head
- Eg. Hagfishes
- The origin of a head opened up a completely new way of feeding for chordates: active predation
- Craniate characteristics: a skull, brain, eyes, and other sensory organs
- Unique to craniates: is the Neural Crest , a collection of cells near the dorsal margins of the closing neural tube in an embryo LE 34-7a Ectoderm The neural crest consists of bilateral bands of cells near the margins of the embryonic folds that form the neural tube. Neural crest cells migrate to distant sites in the embryo. They become parts of the skull, jaw, teeth, dermis and sensory apparatuses. Dorsal edges of neural plate Neural crest Ectoderm Neural tube Migrating neural Notochord^ crest cells An hypothesis for chordate evolution: key characteristics in evolution Notochord Vertebral Column Jaws Amniotic Egg Lungs Legs Craniates
Derived Characters of Vertebrates
- Vertebrates have the following derived characters: - Vertebrae enclosing a spinal cord - An elaborate skull - Fin rays, in aquatic forms
Tetrapods:
Amphibia
Frogs, salamanders, apodans Metamorphosis larval stage – usu. aquatic herbivore w/ gills, lateral line adult – carnivorous w/ lungs, legs Gas exchange through moist skin – require moist environment *Recent rapid decline in populations worldwide
An hypothesis for chordate evolution
Notochord Vertebral Column Jaws Amniotic Egg Lungs Legs
The Amniotes: Amniotic Egg – a key
innovation
- Allowed complete lifecycle on land
- Shell – retains water
- 4 extra embryonic membranes - Amnion - Yolk sac - Allantois - Chorion
Amniotes:Reptilia Lizards, snakes,
Turtles, crocodilians (incl.birds) Scales - (keratin) waterproofing Most lay shelled eggs on land Ectothermy – regulate body temp by controlling exposure to external heat
Amniote Phylogeny
Amniotes: Birds
Flying reptiles Very specialized anatomy for flight Endothermy – maintain body temp through high metabolism Wide variety of lifestyles and ecological roles eg. Important seed dispersers & pollinators New Zealand Birds
Two major groups of animals moved from aquatic to terrestrial environments during evolution. The most important challenges they both had to overcome include:
- A. a need for more protection from predators in the new habitat
- B. a need for increased structural support in the new habitat
- C. a need for faster movement in the new habitat
- D. A need for protection from dessication in the new habitat
- E. Both B and D
- F. All of the above except C
3 Groups:^ Mammalia
Monotremes Marsupials Eutherian Mammals Characteristics Unique to mammals:
Hair (keratin) Mammary glands Differentiation of teeth Large brains, endothermy
Monotremes
- Only extant egg- laying mammals - No placenta
- Hair and milk production
- Echidnas, duck-billed platypus (^) Only in Australia today
Marsupials
- Born early in development, completes development while nursing
- Dominant mammals in Australia
Eutherian Mammals
- Longer pregnancy
- 4 evolutionary lines
- Insectivores
- Herbivores
- Carnivora
- Primates & rodents
Form & Function
Limits to body size, skeletons & movement
As size increases, volume increases more
quickly than surface area
IF l = 5 SA = 150 (1) SA= 600 (1) SA = 1350 (1) SA = 2400 (1) V= 125 (.83) V = 1000 (1.67) V = 3375 (2.5) V = 8000 (3.3)
- Larger, more complex organisms must solve the SA:V problem
- Cnidarians (sac body type) – Body cavity is totally exposed to the environment - thus cells from both body layers are exposed to the environment What about animals with 3 germ/tissue layers?
- Platyhelminthes – body plan is v. flat
- max amount of surface area is exposed to environment
Larger/Complex Animals
- Increased surface area found in particular body tissues
- Flattening, folding, branching patterns are common Fig. 40- 4 0.5 cm (^) Nutrients Digestive system Lining of small intestine Mouth Food External environment Animal body CO (^2) O 2 Circulatory system Heart Respiratory system Cells Interstitial fluid Excretory system Anus Unabsorbed matter (feces)^ Metabolic waste products (nitrogenous waste) Kidney tubules 10 μm 50 μm Lung tissue
- More complex organisms have highly folded/branched internal surfaces for exchanging materials
- In vertebrates, the space between cells is filled with interstitial fluid , which allows for the movement of material into and out of cells - Diffusion in and out of cells requires an aqueous medium of some kind
- A complex body plan helps an animal in a variable environment to maintain a relatively stable internal environment Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
- Most animals are composed of specialized cells organized into tissues that have different functions
- Tissues make up organs , which together make up organ systems Hierarchical Organization of Body Plans Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Animal Tissues
- Different tissues have different structures that are suited to their functions
- Tissues are classified into four main categories: epithelial, connective, muscle, and nervous
Tissue Structure and Function
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Epithelial Tissue
- Epithelial tissue covers the outside of the body and lines the organs and cavities within the body
- Tissue type most associated with exchange of materials
- The shape of epithelial cells may be cuboidal (like dice), columnar (like bricks on end), or squamous (like floor tiles) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings LE 40-5_ EPITHELIAL TISSUE Stratified columnar epithelium Simple columnar epithelium Pseudostratified ciliated columnar epithelium Columnar epithelia, which have cells with relatively large cytoplasmic volumes, are often located where secretion or active absorption of substances is an important function. Stratified squamous Simple squamous epithelia epithelia Cuboidal epithelia
- The arrangement of epithelial cells may be simple (single cell layer), stratified (multiple tiers of cells), or pseudostratified (a single layer of cells of varying length)
Cardiac Muscle
- Found only in the heart, consists of striated
cells electrically connected by intercalated
disks
- Cardiac muscle can generate action
potentials without neural input
Nucleus Intercalated disk 50 μm
Smooth Muscle
- Found mainly in walls of hollow organs, contractions are relatively slow and may be initiated by the muscles themselves
- Contractions may also be caused by stimulation from neurons in the autonomic nervous system Nucleus Muscle fibers 25 μm
Nervous Tissue
- Nervous tissue senses stimuli and transmits
signals throughout the animal
- Nervous tissue contains:
- Neurons , or nerve cells, that transmit nerve impulses
- Glial cells , or glia , that help nourish, insulate, and replenish neurons Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Fig. 40-5n Glial cells Nervous Tissue 15 μm Dendrites Cell body Axon Neuron Axons Blood vessel 40 μm LE 40- 6 Lumen of stomach Mucosa: an epithelial layer that lines the lumen Submucosa: a matrix of connective tissue that contains blood vessels and nerves Muscularis: consists mainly of smooth muscle tissue Serosa: a thin layer of connective and epithelial 0.2 mm^ tissue external to the muscularis Tissues join together to form organs
