4.4 Evolution of the Circulatory System

Question 1

How do unicellular organisms get what they need?

Answer 1

• do NOT require a
  circulatory system
• they meet ALL of their
  needs by DIFFUSION,
  OSMOSIS and TRANSPORT CHANNELS across their cell
  membrane

Question 2

In simple multicellular organisms

Answer 2

→ such as a sponge:
- most of the cells
are CLOSE to the body cavity,

• collar cells with FLAGELLA move water around.
• gases and nutrients are exchanged by DIFFUSION , OSMOSIS and TRANSPORT CHANNELS in the cell membrane.

Question 3

In complex
multicellular
organisms

Answer 3

→ the demands are MUCH
greater and different
transport systems have
evolved.

Question 4

WHAT DOES THE CIRCULATORY SYSTEM
DO???? (4 functions)

Answer 4

1. Transportion:
   circulating nutrients that
   need to get into cells, or out of cells.
   -> Nutrients (glucose, proteins, fats)
   -> Dissolved gases (O2, CO2)
   -> Wastes (methane, ammonia)
   -> Chemicals (minerals, ions)

2.Thermoregulation:
in ENDOTHERMS, blood
distributes THERMAL energy
produced by cellular
respiration to help regulate
internal body temperature.

3.Immune Response:
carrying white blood cells and antibodies to sites of cellular damage to prevent infections.

4. Hormonal Control:
   carrying chemical messengers (called
   hormones) throughout the body to control growth, metabolism, homeostasis and reproduction.

Question 5

Different transport systems (2 types)

Answer 5

Open circulatory system:
Blood or transporting fluid
LEAVES the conducting vessels and bathes the cells before being collected back into receiving tubes.

Example: insects

Closed circulatory system:
Blood is contained WITHIN
conducting vessels throughout its
entire circuit (but various
components move in and out
during its journey)

Example: humans

Question 6

Main components of
circulatory system (3)

Answer 6

1) A FLUID - needed to help molecules move
throughout the organism.

2) A NETWORK OF TUBES - needed to keep the
fluid circulating efficiently

3) A PUMP - needed to keep the fluid moving
continuously.

Question 7

Open CS: (INSECTS AND INVERTEBRATES)
- Are these kind of systems effecient? Why or Why not?

Answer 7

Fluid:
- Colourless HEMOLYMPH (blood crossed with LYMPATHIC system)
- carries nutrients and waste but does NOT carry O2 or CO2.

Hemolymph alternates between bathing the organs in the HEMOCOEL and
moving around the body in blood vessels and the heart.

Tubes:
DORSAL vessel runs the length of the body, hemolymph travels from the
posterior (back) towards the anterior (front).

Pump:

The posterior section of the dorsal vessel is the “HEART”.

• This type of open system is VERY
  inefficient.
• Organisms with open systems have
  very LOW metabolic waste.
• Organisms can’t grow to be very
  big.

Question 8

PATHWAY OF HEMOLYMPH

Answer 8

“HEART” → AORTA → HEMOCOEL → OSTIA (holes in surface of the heart)

Question 9

Closed Simple CS- ANNELIDS

Answer 9

Fluid:
RED BLOOD, carries O2 or CO2.

Tubes:
DORSAL blood vessel, VENTRAL blood vessel and CAPILLARIES to connect them.

Pump:
AORTIC arches, five pairs of muscular tubes that contract and circulate the blood
between the dorsal and ventral vessels.

• Blood must be
  passed through a
  respiratory system
  for gas exchange.

Question 10

Closed Incomplete Double CS (AMPHIBIANS)

Answer 10

Fluid:
RED BLOOD, carries O2 or CO2.

Tubes:
BLOOD VESSELES (arteries and veins).

Pump:
3-CHAMBERED heart; 2 ARTIA (atrium is
singular) and 1 VENTRICLE

The LEFT ARTIUM receives OXYGENATED blood
from the LUNGS.

The RIGHT ARTIUM receives DEOXYGENATED
blood from the BODY CELLS.