7th Grade Science Student ebook

15.3 Vertebrate Structure and Function.

CHAPTER 15: ANIMALS

Other characteristics of vertebrates

Temperature and

chemical

reactions

Most animals need to keep their bodies at a certain temperature.

This is because the chemical reactions inside of their cells can

operate only at temperatures that are neither too hot nor too cold.

Ectotherms Animals that are not able to control their body temperature are

called ectotherms. They are sometimes called cold-blooded. The

body temperature of an ectotherm changes with the temperature of

its environment. When it is cool, some ectotherms warm their

bodies by basking in the sun (Figure 15.21). Nearly all fish,

amphibians, and reptiles are ectotherms.

Endotherms Birds and mammals are endotherms. Endotherms use the heat

produced by the chemical reactions in their cells to maintain a

constant body temperature. Endotherms are sometimes called

warm-blooded. Because they are able to keep their body

temperature warm, many endotherms are adapted to survive in

cold climates.

Fertilization and

development

Vertebrates reproduce sexually and have separate male and female

individuals. Fertilization in vertebrates may occur externally or

internally. In external fertilization, the female lays eggs and the

male drops sperm onto them. Most fish and amphibians use

external fertilization. In internal fertilization, the male deposits

sperm inside of the female. In most reptiles and birds, the female

lays eggs that contain the developing embryo. The eggs hatch and

the young offspring emerge. In some cases, the eggs develop and

hatch inside of the mother. In most mammals, the fertilized egg

becomes an embryo that develops inside of the mother. Then, the

mother gives birth to fully-developed offspring.

Figure 15.21: A lizard basks in the

sun to warm its body temperature.

ectotherms - animals that are

not able to control their body

temperature.

endotherms - animals that use

the heat produced by chemical

reactions in their cells to maintain

a constant body temperature.

external fertilization - the

female lays eggs and the male

deposits sperm on the eggs.

internal fertilization - the male

deposits sperm inside of the

female.