Notes

Let's start with the obvious
They all have DNA and RNA the chemical basis for life. They all require water and food to live. They all reproduce, carrying the genetic material across the generations.

Now how do they differ
Classification: A bacterium is a prokaryote, the others are eukaryotes. Amongst the eukaryotes, the seaweed is an alga, the amoeba is a protist, the mushroom is a fungus, the oak tree is a vascular plant and the person is a mammal.
Habitat
Humans, oak trees and mushrooms live on land, amoeba and seaweed usually inhabit water. Bacteria can grow everywhere.
Reproduction
All species except the human can reproduce asexually as well as sexually. In bacteria, fungi and seaweed, asexual reproduction is more common. The bacterium is able to make a complete copy of itself by cell division, without the need of input of any other genetic material. The reproductive cycle of a bacterium is much shorter (some species as short as 20 minutes).
Metabolism (what they eat and how they obtain their energy)
Put in the sun without food, only the oak tree and the seaweed would be able to survive. Both have chloroplasts which convert the sun's energy into cellular energy that is need to convert carbon dioxide and water into glucose. Fungi are usually able to survive by living off the carbon present in other dead organisms. People and most types of bacteria (except cyanobacteria) need to have a food source (plants, animals).
The oak tree and the human are vascular. Both have specific networks of tubes that transport food, water and gas (oxygen, carbon dioxide) to all parts of the organism. In humans we call these vessels, blood vessels (arteries, vein, capillaries), in plants the tubes that transport water are called xylem and the tubes that transport food (mainly sugars) are called phloem.
Human beings are the only organism that give birth, in which the baby has a completely developed skeleton, urinary system, brain, digestive system at the time of birth. Pollen from the anthers of oak flowers fertilizes the stigma of adjacent oak flowers, in turn producing a seed (acorn) which grows into a new oak tree. What we call mushrooms are the reproductive structures that contain spores, the fungal equivalent of seeds. The majority of the fungus is present as assexual hyphae that is often colourless and cannot be see by the human eye.