Alternating Reproductive cycle of a jelly fish is illustrated. The cyclic illustration is in two stages; Haploid N(orange) and Diploid 2N(Blue).

FIGURE 28–16 Alternating Reproductive Cycles The reproductive cycle of Aurelia, a jellyfish, alternates between asexual and sexual reproduction. A zygote is produced sexually by medusas and grows into a larva. The larva develops into a polyp that buds, reproducing asexually. The polyp releases a medusa.

dd

Internal and External Fertilization

How do internal and external fertilization differ?

In sexual reproduction, eggs and sperm meet either inside or outside the body of the egg-producing individual. These alternatives are called internal and external fertilization, respectively.

Internal Fertilization Many aquatic animals and nearly all terrestrial animals reproduce by internal fertilization. During internal fertilization, eggs are fertilized inside the body of the egg-producing individual.

▸ Invertebrates Invertebrates that reproduce by internal fertilization range in complexity from sponges to arachnids. The eggs of sponges and some other aquatic animals are fertilized by sperm released by others of their species and taken in from the surrounding water. In many arthropod species, males deposit sperm inside the female's body during mating.

▸ Chordates Some fishes and amphibians, and all reptiles, birds, and mammals, reproduce by internal fertilization. In some amphibian species, males deposit “sperm packets” into the surrounding environment; females then pick up these packets and take them inside their bodies. In many other chordate species, males have an external sexual organ that deposits sperm inside the female during mating.

MYSTERY CLUE

A bonnethead.

None of the females in the tank had had contact with a male for three years, long before they were mature enough to reproduce. And female bonnetheads had never been known to store sperm for longer than five months. So what happened?

End ofPage 821

Table of Contents

Miller & Levine Biology
About the Authors
Changing the World of Biology Education
Contents
Diversity of Life: A Visual Guide DOL•1–DOL•64
Labs and Activities
Features
UNIT 1 The Nature of Life
1 The Science of Biology
2 The Chemistry of Life
Unit Project
UNIT 2 Ecology
3 The Biosphere
4 Ecosystems and Communities
5 Populations
6 Humans in the Biosphere
Unit Project
UNIT 3 Cells
7 Cell Structure and Function
8 Photosynthesis
9 Cellular Respiration and Fermentation
10 Cell Growth and Division
Unit Project
UNIT 4 Genetics
11 Introduction to Genetics
12 DNA
13 RNA and Protein Synthesis
14 Human Heredity
15 Genetic Engineering
Unit Project
UNIT 5 Evolution
16 Darwin's Theory of Evolution
17 Evolution of Populations
18 Classification
19 History of Life
Unit Project
UNIT 6 From Microorganisms to Plants
20 Viruses and Prokaryotes
21 Protists and Fungi
22 Introduction to Plants
23 Plant Structure and Function
24 Plant Reproduction and Response
Unit Project
UNIT 7 Animals
25 Introduction to Animals
26 Animal Evolution and Diversity
27 Animal Systems I
28 Animal Systems II
29 Animal Behavior
Unit Project
UNIT 8 The Human Body
30 Digestive and Excretory Systems
31 Nervous System
32 Skeletal, Muscular, and Integumentary Systems
33 Circulatory and Respiratory Systems
34 Endocrine and Reproductive Systems
35 Immune System and Disease
Unit Project
A Visual Guide to The Diversity of Life
HOW TO USE THIS GUIDE
THE TREE OF LIFE
Bacteria
Protists
Fungi
Plants
Animals
Appendices
Appendix A Science Skills
Appendix B Lab Skills
Appendix C Technology & Design
Appendix D Math Skills
Appendix E Periodic Table
Glossary
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q, R
S
T
U
V
W
X, Y, Z
Index
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
Credits
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