The Circulatory System

Which type of organisms do not need a circulatory system because oxygen diffuses directly in and out of their cells?

• Multicellular organisms

• Unicellular organisms

• Complex organisms

• None of the above.

Complex organisms with three cell layers require a circulatory system because their middle layer, the ________, is between the ectoderm and the endoderm and does not come into contact with the external environment.

• Mesoderm

• Ectoderm

• Endoderm

• Cytoplasm

Which of the following is a function of the circulatory system?

• Delivers oxygen from the respiratory system

• Produces hormones

• Digests food

• Filters waste

The circulatory system _______ hormones from the endocrine system.

• A) digests

• B) circulates

• C) absorbs

• D) excretes

Which of the following is a fluid that transports materials through the body?

• Blood

• Water

• Oxygen

• Carbon Dioxide

A network of tubes in which the fluid circulates is known as ______.

• Arteries

• Veins

• Vessels

• Capillaries

What is the mixture of blood and intestinal fluid called in an open circulatory system?

• Plasma

• Hemolymph

• Lymph

• Serum

In an open circulatory system, blood is pumped into body cavities and directly covers the cells. This system is relatively _______.

• efficient

• inefficient

• high pressure

• closed

What is an open circulatory system?

• A system where blood stays within blood vessels

• A system where blood does not stay within blood vessels

• A system found only in mammals

• A system that provides rapid delivery of materials.

In an open circulatory system, blood does not stay within the blood vessels. Which of the following organisms typically have this type of system? (Choose one)

• Humans

• Grasshoppers

• Birds

• Fish