BIO 180 Lecture 15:02

found in descendants modern reptiles birds egg

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: terrestrial forms. - Found in descendants: modern reptiles, birds, egg-laying mammals. What is an Amniotic Egg and what does it do? - provides water, nutrients & mechanical support - 3 internal membranes (extra S.A. -> efficient diffusion -> *larger eggs) - leather or calcified shell. Variation in Egg-Laying Strategies 1. Oviparous * - Most fish & amphibians, all birds – why? 2. Ovoviviparous - Give birth to live young. * - Most sharks, some lizards & snakes. 3. Viviparous - Give birth to live young. * - Most mammals. Placenta - Organ rich in blood vessels that facilitates transfer of oxygen and nutrients from mother to developing offspring. - Derived from maternal and embryonic tissues (chorion, allantois) Ex. Sharks show entire range. Advantages of Viviparity & Placenta 1. 2. 3. Disadvantage? Parental Care - Parental care particularly extensive in mammals and birds. - Mammals evolved lactation – produce milk to feed offspring....
View Full Document

Ask a homework question - tutors are online