Biodiversity Then and Now


Focus  Comparing biodiversity in the ocean over time


Focus Question

How does the advancement of oceanographic sampling techniques change how scientists look at biodiversity?


Learning Objectives

Students will compare indices of biodiversity between H.M.S. Challenger expedition and the Mountains in the Sea mission.


Students will graph and analyze a data set.



Internet access

Sampling worksheet

Graph paper


Audio/visual Materials



Teaching Time

One 45-minute period


Seating Arrangement

Individually or in small groups


Maximum Number of Students



Key Words

H.M.S. Challenger



Deep water corals


Background Information

This lesson is part of the "New Challenger Series" developed by the College of Exploration.  The series can be found at


This lesson is a comparative study between the historic voyage of the British sailing ship H.M.S. Challenger, conducted between 1872-1876 and the Mountains in the Sea mission of 2003, using the Alvin submersible.  Scientists involved in both missions were studying the biodiversity, or the "diversity of life" in our oceans, even though they had technologically diverse ways of doing so.


The Challenger expedition is often considered to be the first one undertaken specifically to conduct oceanographic research.  The Challenger had the very broad assignment from the British government to study the physical and biological conditions of the oceans.  This around-the-globe voyage covered almost 69,000 nautical miles and gathered data on temperature, currents, water chemistry, marine organisms, and bottom deposits at 362 oceanographic stations. The trip took 3½ years.  Samples were taken using trawls, which are nets towed behind a boat to collect organisms. The Challenger crew employed a trawl lined with fine linen or cotton that was changed after every haul. Lead weights of 28 pounds each were hung across the top to ensure that the trawl dragged across the bottom.  The crew also used a dredge, different from the trawl in that it was weighted and dragged along the bottom in order to dig into the sediment and sample substrate and the creatures that inhabited it.  However, they could not be sure at what depth the organisms they caught came from, as the animals could have been captured as the trawl was being brought up from the depths.


The 2003 Mountains in the Sea mission had the specific mission of exploring Atlantic seamounts, which are the remains of underwater volcanoes that are islands of productivity compared to the surrounding environment.  The specific mission of this expedition was to map, collect, and identify deep water corals, fishes, and miscellaneous invertebrates from the seamounts.  With the development of deep diving submersibles such as ALVIN, selectivity has been added to undersea sampling abilities.  The submersible’s manipulator arm and suction sampler are often capable of choosing individual samples that a scientist is interested in. ALVIN also is equipped with a suction sampler that is used to collect animals under gentle suction and deposits them into a container.

Learning Procedure


1.  Using the internet, ask students to research five of the phyla on the Sampling worksheet and write down an example of an organism from each of the phyla they chose.  (If internet is not available, teachers may want to have students do their research in the library.)


2.  Explain the backgrounds of the two missions that will be compared. Discuss how the sampling gear differed, and how undersea technology has advanced.  (For more detail on tools and technologies used, please refer to the lesson in the Challenger Series titled "So What's Different? Exploring the Oceans Then and Now.")


3.  Ask students to refer to the Sampling Results worksheet.  Have them total the number of samples from each ship.  Then, for both cruises, have students determine what percentage of the total sample each phylum represents.  For example, Cnidaria for Challenger would be 16/88 x 100 = 18% of all the phyla.


4.  Using either the graph paper or the computer, have students create a bar graph of this data from both cruises, plotting the Phyla on the x-axis and the percent of each phylum in the total sample on the y-axis.  If  both ships have a phylum in common, make two bars side by side (one for the Challenger data, and a bar right next to it for the Atlantis data).  Ask students to answer the following questions:  Which phylum was most abundant on each cruise? Overall?  What are some possible reasons for this conclusion?  Which cruise had more biodiversity (larger number of different phyla represented)?  Why?  Students should recognize the differences in the missions of the two cruises, the sampling technologies, differences in location of the two sites, and that the shape/geology of the seafloor plays a role.  For example, the Atlantis samples were taken on a seamount, while Challenger's were not.  Students should present their data and explanations to the class (individual or groups) and show their bar graphs (overheads or power points) along with the phyla they researched.


5.  Ask students to write down their thoughts as to whether, based on these two samples, any conclusions can be drawn about changes in biodiversity from the 1800's to today.   Have them defend their opinions.


The BRIDGE Connection

Under Ocean Science Topics, Biology. Or search for "biodiversity".


The "Me" Connection

Ask students to discuss in small groups why they should care about changes in biodiversity on land and in the ocean.


Connections to Other Subjects

History, Language Arts, Mathematics



For individual evaluations, have students prepare written interpretations of the summarized data prior to leading a group discussion.



Have students use the internet to research the concept of biodiversity in terrestrial habitats (forests, grasslands) and also in aquatic habitats. Ask them to work in groups and create a presentation where they compare our general knowledge of terrestrial biodiversity to what we know about oceanic biodiversity. Which type of biodiversity (terrestrial or oceanic) do they think scientists are more informed about? Why?  (See Resources section below for web links.)



NOAA Ocean Explorer Website -- Mountains in the Sea mission


College of Exploration's Challenger Website

(See the "New Challenger Series" lessons for the classroom) 


The Challenger Society for Marine Science



What is Biodiversity? (Rutgers University)


Center for International Environmental Law Wildlife and Biology Program


NOAA's Protected Resources Website


National Science Education Standards

Content Standard A:   Science as Inquiry


Content Standard C:  Life Science


Content Standard E:  Science and Technology


Content Standard F:  Science in Personal and Social Perspectives


Content Standard G:  History and Nature of Science



This lesson was created by Melissa Ryan of the College of Exploration, and Diana Payne of Connecticut Sea Grant.


Challenger and Mountains in the Sea Sampling Results

Number of Specimens at Sampling Station


 Phylum Challenger Mountains in the Sea
Cnidaria 16 52


Echinodermata 11 18
Arthropoda 3 6
Nemertea 1 0
Annelida 10 24
Foraminifera 0 2
Chordata 0 4
Porifera 0 7
Bacillariophyta 45 0


2 7
Anthomastis 0 10
Pogonophora 0 1