Ch 19 Notes - Chapter 19 Speciation and Macroevolution lec...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 19 Speciation and Macroevolution lec 4 (all of chapter 19 covered) 4-18-06 *about 10-100 million species of animals. *1.8 million named and described species - distinct kind of organism; latin for “kind” taxonomy - the science of naming, classifying, and describing animals *Linnaeus used morphological species concept for taxonomy. -is not adequate biological species concept - Mayr; “a species consists of one or more populations whose members interbreed in nature to produce fertile offspring and are reproductively isolated from other species. In other words, each species has a gene pool separate from other species and reproductive barriers restrict one species from interbreeding with other species. *problem is it applies to only sexually reproducing animals. *also species do sometimes interbreed such as zebra and donkey evolutionary species concept - aka phylogenetic species concept ; species emerge where population has gone through evolution long enough for statically significant differences in diagnostic traits to emerge. *problem is not all histories of taxonomic groups have been studied **species in text refers to biological species concept REPRODUCTIVE ISOLATION 1. explain the significance of reproductive isolating mechanisms, and distinguish among the different prezygotic and postzygotic barriers. reproductive isolating mechanisms - prevent interbreeding between two different species whose ranges (areas where each lives) overlap; gene flow is prevented. Prezygotic barriers interfere with ferilization prezygotic barriers - reproductive isolating mechanism that prevent fertilization from taking place. Thus, interspecific zygote – a fertilized egg by union of two different species—never occurs. Includes temporal, habitat, behavioral, mechanical, and gametic isolation. temporal isolation - caused by reproduction occurring at different times of day, season, or year. ex: frogs habitat isolation - caused by living in different habitats, although geographic region may be close. ex: some birds live in tree, others live in low ground swamp. behavioral isolation - aka sexual isolation ; caused by differences in exchange of signals before mating. ex: vocalization, displays, courtship,
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
mechanical isolation - caused by incompatible structures of genital organs. ex: in flowers only certain bees are able to help in reproduction. if bee is different then it’s incompatible. *temporal and mechanical seem to have a high correlation gametic isolation - caused by molecular and chemical differences in which different species’ eggs and sperm are incompatible. very rare to have interspecific fertilization in marine animals. also pollen has molecular recognition to not germinate on stigma of different plant species. postzygotic barriers prevent gene flow when fertilization occurs
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 6

Ch 19 Notes - Chapter 19 Speciation and Macroevolution lec...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online