Chapter 5 Introduction to Primates

Chapter 5 Introduction to Primates - Chapter 5:...

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Chapter 5: Introduction to the Primates Two Reasons to Study Primates - Reasoning by homology o Closely related species tend to be similar morphologically due to the fact that they retain and share traits acquired through descent from a common ancestor Viviparity (bearing live young) and lactation are traits that all placental and marsupial mammals share - Reasoning by analogy o Natural selection leads to similar organisms in similar environments By assessing the patterns of diversity in the behavior and morphology of organisms in relation to their environments, we can see how evolution shapes adaptation in response to different selective pressures Primates are our closest relatives - The fact that humans and other primates share many characteristics means that other primates provide valuable insights about early humans o Humans are more closely related to primates than to any other species We have the same well-developed visual abilities and grasping hands and feet We also share extended periods of juvenile development and larger brains in relation to our body size - So, nonhuman primates provide useful models for understanding the evolutionary roots of human morphology and for unraveling the origins of human nature Primates are a diverse order - Diversity within the primate order helps us to understand how natural selection shapes behavior o Animals that are closely related to one another phylogenetically tend to be very similar in morphology, physiology, life history and behavior Differences among closely related species are likely to represent adaptive responses to specific ecological conditions Similarities between distantly related creatures living under similar ecological conditions are likely to be the product of convergence This approach is called the comparative method Ex: the observation that there are substantial differences in male and female body size in species that form nonmonogamous groups suggests that highly dimorphic hominins in the past were not monogamous o Sexual dimorphism: morphological differences between males and females Features that Define the Primates - The primate order is g en erally d efined by a nu m b er of shared, derived characters, but not a share all of thes e traits - Primates are a rather nond escript m a m m alian order that cannot be una m biguously charact single d erived feature shared by all m e m b ers o The big toe on the foot is opposable and the h ands are preh ensile o There are flat n ails on the hands and feet in m ost species inste ad of claws. There are als tactile p ads with fingerprints on fingers a nd toes o Locomotion is hindlimb do minat ed o There is a n unsp ecialized olfactory a pp aratus that is reduced in diurnal primates o The visual sense is highly developed. The ey es are large a nd m oved forward in the h e a d stereoscopic vision This gives the m depth p erception o Females h ave s m all litters, a nd g estation a nd juvenile p eriods are longer than in other m
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Chapter 5 Introduction to Primates - Chapter 5:...

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