BI 101: Chordate Animals & Biodiversity Final Exam tomorrow Announcements Same time, same place Review Mary s Peak biodiversity results Lab 10 today 1
Deuterostome Development 2
Phylum Chordata Contains both vertebrates AND invertebrates! All Chordates share four characteristics: 1. Dorsal nerve cord 2. Notochord (Primitive skeleton) 3. Pharyngeal gill slits 4. Post-anal tail Chordates: Homologous features 3
Human Embryo features 4 chordate features. Boney skeleton 4
Tunicates Fig. 26-3a, p.434 Tunicates Lack the backbone that is found in vertebrates. Have a nerve cord and all other chordate features. 5
Lancelets 6
Existing Jawless Fishes Cylindrical body No paired fins Cartilaginous skeleton Hagfish tentacles gill slits (twelve pairs) mucous glands Lamprey gill openings (seven pairs) Hagfish: the first Craniate Derived adaptation: Skull Cartilage plates help protect brain Jawless fish Resemble lancelets and vertebrates Endoskeleton not hardened with minerals as in vertebrates Nearly blind!, burrowers, scavengers, slime! Arose before 530 million years ago Fig. 26-5a, p.435 7
Lampreys are jawless vertebrates Derived adaptation: Vertebral column Have a spinal cord protected by segments of cartilage tube & protection Known as backbone Class: Petromyzontida 8
Discussion: Primitive(jawless) fish have seven gills, while most modern (jawed) fish have only five. How could this be explained in an evolutionary perspective? Hypothesis for the evolution of vertebrate jaws 9
Cartilaginous Fishes: Class Chondrichthyes Most are marine predators Cartilaginous skeleton Main groups: Skates and rays Sharks Chimaeras (ratfishes) 10
Bony Fishes: Class Osteichthyes Includes 96 percent of living fish species Two subclasses: Ray-finned fishes Lobe-finned fishes 11
Lobe-Finned Fishes Coelocanths: Have gills Lunglike sacs do not function in gas exchange inside lobed fins, bony or cartilaginous structures undergoing modification Lobe-Finned Fishes Lungfish: Have gills and one lung or a pair Must surface to gulp air Fig. 26-10b, p.439 12
limb bones of an early tetrapod Fig. 26-10e, p.439 13
Mary s Peak biodiversity results Diversity Index: A mathematical model of biodiversity, taking into acount the relative amount of each species Shannon's diversity index (aka the Shannon-Wiener index, Shannon-Weaver index) R= species richness p i = proportion of species i Biodiversity results Discuss with your group and write an observation and/or conclusion on the whiteboard when done: Take a look at the compiled data and results What are some observations you make? What are some conclusions? 14
Discussion You are discussing biodiversity and extinction with your friend, who is skeptical about using valuable time and money conserving rare species. He/She points out that 99% of all species that have ever existed have gone extinct. Thousands of species have already gone extinct since life began on Earth. Even though many species are going extinct now, I don t think it matters. Despite this statement, why might species extinction still be a problem? Mass Extinctions: rate of extinction Background extinction rate 15
Discussion: Scientists estimate that in the last 400 years more than a thousand species have become extinct. This rate is 100 to 1,000 times the usual background rate found in the fossil record. What does this information imply? Mass extinctions: Consequences Long recovery time Typically 5-10 million years 100 million years after Permian mass extinction Alter ecological communities Changes in dominant species Changes in predator/prey Adaptive radiation 16
Mass extinctions: Altering ecological communities Mass extinctions: Adaptive radiation Periods of fast evolutionary change Species evolve to fill ecological roles, or niches Drosophila, Fruit fly 17
Mass extinctions: Adaptive radiation Periods of fast evolutionary change Species evolve to fill ecological roles, or niches Common on islands 18