1. Introduction:

a. Describe the Tiktaalik fossil and its importance.

b. Name and describe the two items do homeostatic mechanisms show:

2. Continuity:

a. What does our excretory system do?

1. Introduction

     a. The Tiktaalik is a fossil that existed about 12 million years before the first tetrapods.

    b. The items homeostatic mechanisms show are continuity and change.

2. Continuity

       a. Our Excretory system is the system responsible for the discharging of waste products from the body.

Explanation:

1 a. Tiktaalik fossil (Tiktaalik roseae), also known as the "fishapod," is a 375 million year old fish fossil  discovered in 2004 in the Canadian Arctic. The fossil displays a mixture of fish and amphibian traits (i.e the pioneer tetrapods). Those tetrapod features in the Tiktaalik marks the earliest appearance of these features in fossil record.

Importance: The discovery of the Tiktaalik fossil explains  a crucial point in the history of life on Earth: i.e it sheds light on when the very first fish ventured out of the water onto land.

b. Continuity in homeostasis implies common ancestry or homology. For example the excretory system in flatworms, earthworms and vertebrates basically serves the same function, and has remained unchanged (save for a few tweaks), over the last few million years.

Change implies changes in the environment which causes changes in homeostatic mechanisms. For example the transition of aquatic animals from water to land which necessitates changes in their respiratory mechanisms.

2. Continuity

a. The excretory system is the system of an organism's body that is responsible for the function of excretion, the process of eliminating bodily wastes produced by homeostasis.

The mechanisms of homeostasis are body temperature, body fluid composition, blood sugar, gas concentrations, and blood pressure.

The organs that are involved in this process of waste elimination are the sweat glands, the liver, the lungs and the kidneys.