BIOLOGY Life on Earth WITH PHYSIOLOGY Tenth Edition

BIOLOGY Life on Earth WITH PHYSIOLOGY Tenth Edition Audesirk Byers 1 An Introduction to Life on Earth Lecture Presentations by Carol R. Anderson Westwood College, River Oaks Campus © 2014 Pearson Education, Inc.

Chapter 1 At a Glance What Is Life? © 2014 Pearson Education, Inc.

1. 1 What Is Life? Biology comes from the Greek words “bio” meaning “life” and “logy” meaning “the study of. ” Organisms share common characteristics that, taken together, define life. Organisms: § Acquire and use materials and energy § Actively maintain organized complexity (made of cells) § Perceive and respond to stimuli § Grow § Reproduce § Have the capacity to evolve, collectively § Homeostasis © 2014 Pearson Education, Inc.

1. 1 What Is Life? § The cell is the basic unit of life – It is separated from its surroundings by a membrane – It encloses a variety of structures and chemicals in a fluid environment © 2014 Pearson Education, Inc.

Figure 1 -1 The cell is the smallest unit of life nucleus cell wall

1. 1 What Is Life? § Organisms acquire and use materials and energy – Materials and energy are required for organisms to maintain organization, to grow, and to reproduce – Important materials (minerals, water, & other simple chemical building blocks) are acquired from the air, water, soil, and bodies of other living things – Organisms use energy continuously to sustain themselves © 2014 Pearson Education, Inc.

Figure 1 -2 Properties of life Antennae and eyes: living things respond to stimuli

1. 1 What Is Life? § Organisms acquire and use materials and energy (continued) – Organisms obtain energy in two ways, coming directly or indirectly from the sun – Photosynthesis is the process by which plants and some single-celled organisms capture sunlight – Other organisms consume energy-rich molecules in the bodies of other organisms © 2014 Pearson Education, Inc.

Figure 1 -3 The flow of energy and the recycling of nutrients © 2014

1. 1 What Is Life? § Organisms actively maintain organized complexity – Living things use energy on a continuous basis to selfsustain – Cells pump chemicals in and out for appropriate chemical reactions to occur – Organisms maintain relatively constant internal conditions or homeostasis © 2014 Pearson Education, Inc.

Figure 1 -4 Organisms maintain relatively constant internal conditions © 2014 Pearson Education, Inc.

1. 1 What Is Life? § Organisms perceive and respond to stimuli and maintain homeostasis – Organisms sense and respond to internal and external environmental stimuli – Sensory organs in animals can detect and respond to external stimuli such as light, sound, chemicals, etc. – Internal stimuli in animals are perceived by stretch, temperature, pain, and chemical receptors – Plants and bacteria respond to stimuli as well (e. g. , plants grow toward the light, and bacteria move toward available nutrients in a medium) © 2014 Pearson Education, Inc.

1. 1 What Is Life? § Organisms grow – Every organism becomes larger over time – Plants, birds, and mammals grow by producing more cells to increase their mass – Bacteria grow by enlarging their cells; they divide in half to reproduce after genetic material is copied – Growth involves the conversion of acquired materials to molecules of the organism’s body © 2014 Pearson Education, Inc.

1. 1 What Is Life? § Organisms reproduce – Organisms reproduce by dividing in half, producing seeds, bearing live young, and laying eggs – Organisms give rise to offspring of the same type – The parent’s genetic material (DNA) is passed on to the offspring, creating continuity of life © 2014 Pearson Education, Inc.

Figure 1 -6 Organisms reproduce Dividing Streptococcus bacterium © 2014 Pearson Education, Inc. Dandelion

Figure 1 -7 DNA © 2014 Pearson Education, Inc.

1. 1 What Is Life? § Organisms, collectively, have the capacity to evolve – Evolution is the process by which modern organisms descended, with modifications, from preexisting forms of life – Changes in DNA within populations occur over the course of generations, which results in evolution – Populations are groups of the same type of organism living in the same area © 2014 Pearson Education, Inc.

1. 2 What Is Evolution? § Evolution explains the diversity of life on Earth § Evolution provides an explanation for the similarities found among different types of organisms – Chimpanzees and people have various physical features in common – DNA of humans differs from that of chimpanzees by less than 5% © 2014 Pearson Education, Inc.