The basic units of life on earth

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Biology 211 Homework#1

The basic units of life on earth

Complex living things (organisms) like plants and animals are made up of characteristic structures.   Individual cells contain genetic information (DNA) that allows them to reproduce themselves and be the kind of cells they are genetically programmed to be (this varies enormously depending on the complexity of each organism).

Tissues are groups of cells that arrange themselves to create structures.  Organs are made of different types of tissues, which together work to create structure and function for the organism.


Most of the living things on earth (in terms of numbers) consist of a single cell, and do not make complex cellular structures.


But all living things have an enormous amount in common in terms of how cells work to reproduce and survive.  Therefore, they can be fairly easily organized in terms of what they have in common in their DNA, which tells a story about the evolutionary relationship of all living things.


1)  There are hundreds of thousands of different types of living things on this planet.  Each of these living things has been categorized so that it belongs in one of three…  (BOLD the correct answer)


(a) domains     (b) genera (plural of “genus”)    (c) kingdoms    (d) species



2)        (a) List the three domains of life.


(b) Two of the three domains you listed in part a are comprised almost entirely of relatively simple single-celled organisms.  What are these two domains?



(c) Consider the domain you did NOT list in part b.  Does this domain include any type of single-celled organisms? (BOLD the correct answer)   Yes    or    No



3)  Consider your answer to question #1.


(a) In which domain are animals (including humans) classified?



(b) In which domain are plants classified?



4)  Organisms that are the most related to one another (generally, so related that they may successfully breed with one another) are said to be part of the same… (BOLD the correct answer)


(a) domain    (b) kingdom   (c) species


For most of this quarter, we will focus on eukaryotic cells (if you ever take microbiology, that’s where you’ll learn all about prokaryotic cells).  The following questions will help you learn some basic things about eukaryotic cells.


5)  Animal cells and plant cells are both classified as…  (BOLD the correct answer)


Prokaryotic    OR    Eukaryotic



6)    Which type of cell has a cell (plasma) membrane?(BOLD the correct answer)


Animal cell   OR   Plant cell   OR   Both


Which type of cell has a plasma membrane and a cell wall?(BOLD the correct answer)


Animal cell   OR   Plant cell   OR   Both


Which type of cell appears to have a sturdier outer covering?(BOLD the correct answer)


Animal cell   OR   Plant cell


Which type of cell contains organelles that convert energy from the sun into a form of energy that the cell can use directly? (BOLD the correct answer)


Animal cell   OR   Plant cell   OR   Both


What’s the name of the organelle that can produce sugar (stored chemical energy)?



Which type of cell contains mitochondria?(BOLD the correct answer)


Animal cell   OR   Plant cell   OR   Both


Which type of cell contains a central vacuole?(BOLD the correct answer)


Animal cell   OR   Plant cell   OR   Both


7)  The most simple and abundant cells on earth do not have any intracellular membranes or complex intracellular structures.  But they contain DNA which codes for their reproduction and survival, and they have cell membranes much like more complex organisms.  What is the single cellular structure other than DNA or membranes surrounding the cell, that single celled organisms have in common with more complex organisms?






8)  What does symbiotic mean?




9)  What does the “Endosymbiotic theory” explain about different types of Eukaryotic cells?





10)  Why do you think that Eukarytic cells evolved to surround their DNA with a biological membrane?

Last Updated on September 30, 2019