Chapter 42.1 Flashcards
What must every organism do?
Exchange materials with its environment
How do exchanges usually occur?
at the cellular level by crossing the plasma membrane
How do exchanges occur in unicellular organisms
directly with the environment
An example of a specialized exchange system in animals
gills - O2 diffuses from the water into blood vessels and CO2 diffuses from blood into the water
How do small molecules move between cells and their surroundings?
diffusion
Why is diffusion only efficient over small distances
the time it takes to diffuse is proportional to the square of the distance - thus diffusion time increases exponentially with distance
How do most animals exchange materials with the environment
a fluid-filled circulatory system
What does a gastrovascular cavity funcion in?
the digestion and distribution of substances throughout the body
What does a circulatory system have?
- a circulatory fluid
- a set of interconnecting vessels
- a muscular pump (heart)
The circulatory system connects the fluid that surrounds cells with the organs that:
- exchange gases
- absorb nutrients
- dispose of wastes
In insects, other arthropods, and some molllusce, what is the circulatory fluid called?
Hemolymph
Hemolymph
bathes the organs directly in an open circulatory system
What has closed circulatory systems?
Annelids, cephalopods, and vertebrates
What is the closed circulatory system of humans and other vertebrates called?
the cardiovascular system
The three main types of blood vessels
arteries, veins, and capillaries
