College Level Biology

Page 218

is in the small intestine where the vast majority of food is absorbed, particularly the jejunum, which is the middle segment of the small intestine. The food that is not absorbed is eliminated through the large intestine and the anus.

RESPIRATORY SYSTEMS The goal of the respiratory system is to exchange oxygen and carbon dioxide between the animal and the environment. Animals breathe both voluntarily and involuntarily. The amount of air taken in and the rate of breathing is regulated mainly by the brain’s respiratory system. There is inhalation and exhalation. Inhalation fills the lungs with oxygenated air. The oxygen reaches alveoli which are small sacs that exchange the oxygen with carbon dioxide, deep within the lungs. Outside of the lungs, cellular respiration takes place, in which oxygen participates in the breakdown of glucose into CO2, making ATP in the process. Evolutionarily speaking, there has been a change in the way organisms allow for oxygen and carbon dioxide exchange. As the animal complexity and size has increased, the respiratory system developed structures (the alveoli) with a large surface area in order to allow for the maximal rate of diffusion. The diffusion process is completely passive and goes from an area of high concentration of oxygen and carbon dioxide to a lower concentration of these gases. For small multicellular organisms, diffusion across an outer membrane is enough to meet their oxygen needs. This works only up to a one-millimeter distance from the cell to the exterior of the animal. This is how flatworms and cnidarians operate; they are flat or tubular so every cell participates in gradual diffusion across the cells. Other than lungs and diffusion, animals have developed other effective ways to have gas exchange. Earthworms and amphibians respire through their skin. There is a dense interconnected capillary network just below the skin that helps participate in gas exchange. It requires that the skin be moist in order to have gases dissolve and diffuse across this surface. Water-living organisms use oxygen dissolved in water. Fish and other aquatic organisms will use gills in order to extract oxygen from the surrounding water. Water passes over 210


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Summary of the Course

5min
pages 250-252

Quiz

3min
pages 246-249

Key Takeaways

0
page 245

Ecosystems

3min
pages 239-240

Population Ecology

3min
pages 241-242

Quiz

3min
pages 232-235

Key Takeaways

0
page 231

Respiratory Systems

3min
pages 218-220

Endocrine Systems

3min
pages 225-226

Immune Systems

5min
pages 221-224

Reproductive Systems

6min
pages 227-230

Digestive Systems

1min
page 217

Nervous Systems

2min
pages 215-216

Quiz

3min
pages 209-211

Key Takeaways

0
page 208

Fungal Reproduction

2min
pages 203-204

Fungal Physiology

1min
page 202

Fungal Anatomy

5min
pages 198-201

Ecology of Fungi

3min
pages 205-207

Quiz

2min
pages 193-196

Plant Biotechnology

0
page 191

Key Takeaways

0
page 192

Transpiration

3min
pages 189-190

Fruits

1min
page 187

Pollination

2min
pages 185-186

Soil Utilization and Plant Nutrition

2min
page 188

Flowers

0
page 184

Quiz

2min
pages 173-176

Reproduction of Plants

1min
page 183

Plant Morphology

3min
pages 180-182

Key Takeaways

0
page 172

Protista

5min
pages 164-168

The Different Animal Phyla

3min
pages 169-171

Quiz

3min
pages 152-155

Archaea

6min
pages 160-163

History of Evolution on Earth and Origin of Species

11min
pages 143-150

Key Takeaways

0
page 151

Modern Synthesis in Evolution

3min
pages 141-142

Natural Selection

7min
pages 137-140

Quiz

3min
pages 132-135

Genome

1min
page 127

Regulation of Gene Expression

3min
pages 128-130

Gene Mutations

1min
page 126

Chromosomes and Genes

3min
pages 124-125

DNA and Genetics

1min
pages 122-123

Dominant Inheritance

1min
page 120

Quiz

2min
pages 112-115

Key Takeaways

0
page 111

Chloroplasts

3min
pages 108-110

Photosynthesis

4min
pages 105-107

Fermentation

2min
pages 102-104

Oxidative Phosphorylation

4min
pages 99-101

Glycolysis

5min
pages 94-97

Quiz

3min
pages 90-92

Krebs Cycle or Citric Acid Cycle

0
page 98

Meiosis

1min
pages 86-88

Mitosis

1min
page 85

The Cell Cycle

1min
page 84

Mitochondrial Physiology

1min
page 82

Endoplasmic Reticulum

0
page 77

Nucleus

1min
page 76

Organelles

1min
page 74

Cytoskeleton

0
page 75

Key Takeaways

0
page 67

Bacterial Motility

1min
page 66

Quiz

2min
pages 68-71

Prokaryote Cell Division

2min
page 65

Classifying Bacteria

1min
page 64

Bacterial Genetics

1min
page 62

Bacterial Physiology

1min
page 61

Bacterial Communication

1min
page 63

Quiz

3min
pages 53-55

Prokaryote Structure

5min
pages 57-60

Non-Human Viral Infections

2min
pages 50-51

Epidemics from Viruses

1min
page 48

The Virome

1min
page 43

Virus Replication

3min
pages 44-45

Viruses and Disease

1min
page 47

Origins of Viruses

1min
page 38

The Replication of the Viral Genome

1min
page 46

Viral Structure

3min
pages 39-42

What is a Virus?

1min
page 37

Proteins

2min
pages 24-25

Nucleic Acids

1min
page 26

Quiz

2min
pages 31-34

Key Takeaways

0
page 30

Water and Biology

3min
pages 27-29

Organic molecules

3min
pages 19-20

Lipids

2min
pages 22-23

Preface

5min
pages 9-11
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