Welcome! In this online module, you will explore the components that contribute to biodiversity, how it is measured, and the value it plays in keeping earth alive and healthy. The following material was adapted from the concept guide linked below. Follow along with the sections excerpts in-order to optimize your experience.
Section 1.0 A Preview of Biodiversity
Task 1: Read the article excerpts below to answer the following questions.
The term biodiversity refers to the multitude of living species on Earth and their incredible variations. There are no exclusions for organisms when describing total global biodiversity, meaning organisms from all three domains of life are included. These domains are referred to as Bacteria, Archaea, and Eukarya. The relationships of these groups can be seen in the image below.
Members of Eukarya include eukaryotic organisms such as plants, animals, protists, and fungi. Archaea includes organisms such as retroviruses (Ebola/Marburg), and bacteria includes microbes such as E. Coli (a common cause of food poisoning). Archaea are unicellular organisms that lack a true nucleus (organelle that contains the genetic information of an individual), which distinguishes them from their nucleated counterparts Eukarya and Bacteria.
Despite sharing similarities when compared to Archaea, members of Eukarya differ from Bacteria as these organisms are multicellular and have their organelles (functional parts of the cell) surrounded in individual membranes. Members of Archaea are commonly represented by those organisms that live in extreme conditions such as in the Dead Sea (‘salt-loving’ halophiles) or in volcanoes (‘heat-loving’ thermophiles).
Task 1: Concept Check!
Task 2: Read the excerpt below to answer the following questions.
Depending on the ecological system being described or studied, the scope of biodiversity might be confined to a particular location or groups of locations. When we describe the biodiversity of organisms at one particular location, we refer to this as an assessment of alpha diversity (α diversity). This measurement is particularly useful for understanding what mixture of species are present within an area.
For example, if you were to measure the alpha diversity of a park in city of Chicago, you may include up to a mixture of 155 species of birds depending on the location of the park, numerous insect species, plant species, etc. Regardless of the type of species, because we have established our area of study as the park, every living species within the park will be included in the alpha diversity assessment.
C) Penn State | Insect Biodiversity Center
When multiple locations are taken into consideration, this becomes what is considered a beta-diversity (β diversity) assessment. This type of assessment can be incredibly useful when assessing large regions for biodiversity. For example, β diversity is beneficial for assessing the biodiversity of a country, or a large region of land such as a state. In this application, alpha assessments are taken at many different habitats, and compiled in a beta diversity application.
The scenarios given above for α and β diversities involve looking at an ecosystem level. These terms can, however, be applied to smaller scales, for instance looking at the biodiversity among a certain species (either from observable characteristic or genetic differences).
Task 2: Concept Check!
Task 3: Watch the video segment below (survey of relevance optional)
This video looks at species diversity within ants in the Gorongosa National Park (Mozambique, Africa).
Section 2.0 How does Biodiversity Arise?
Task 4: Read the excerpt below, then watch the associated video.
A Chance Mutation Can Lead to Variation
Within every organism, there is a sequence of genetic information that makes up every characteristic of that individual. From time to time, sequences must copy themselves in order to create new cells or pass on genetic information. A nature-made machine, editing enzymes are not perfect and occasionally make errors. These mistakes involve either adding in a base pair that doesn’t below (e.g., AATCG becomes AATGCG), removing a base pair altogether (e.g., ACGT becomes AGT), or swapping one base pair with another (e.g., ACCT becomes ACCG). Changes such as these can be fatal depending on the location of the change, or can have no effect on function. Occasionally, errors (also known as mutations) can alter a function within the organism without being fatal, resulting in a change of a visible characteristic. If these mutations are heritable (or within the cells to be used during fertilization), they can be passed on to new generations.
With new genetic potential, if a particular change in function is beneficial to an organism, these characteristics boost this individual’s chance for survival–heightening its chance of passing along this beneficial mutation to more offspring. Over time, accumulation of desirable characteristics in a population begin to shift the genetic pool available during mating events. Through directional selection, or a movement toward a beneficial trait in a population, these organisms become more similar to each other at the sequence where the mutation occurred. Errors in sequencing will continue over time, and those that occur in heritable cells (sperm, egg, etc.) might allow for survival against a new environmental factor, contributing to further shifting in genomic patterns and eventually allowing for the possibility of a new species with unique traits to emerge.
With enough geographic isolation or lack of gene immigration from outside populations, mutations in a population accumulate and eventually can cause populations of what were once the same species to now be genetically distinct enough to be considered different species.
See the video below for a visual demonstration of this concept.
Task 5: Read the excerpt below and watch the associated video.
How do external pressures affect an organism’s survival, future generations?
In the context of mammals, after the mass extinction of dinosaurs in the Cretaceous period (estimated 145.5 million years ago) a wide range of habitats became available for surviving creatures to colonize. One lineage became especially adapted to new modes of life, eventually extending a branch providing us humans (Homo sapiens) the opportunity to wonder about these foundational moments in history.
See the video below for a visual demonstration of this concept.
Task 6: Read the excerpt below and watch the associated video.
Perhaps one of the most cited examples of colonization into new habitats is a case of adaptive radiation in Darwinian Finches (1800s). The term adaptive radiation refers to the same logic we set forth earlier, stating that organisms that invade available niches will have selective pressures from the environment on traits that encourage their success. Organisms with beneficial mutations or heritable abilities will survive, pass on their genetic information, and in turn a new species of organisms can emerge over time, now adapted to this new habitat.
See the video below for a visual demonstration of this concept.
HHMI BioInteractive video on evolution in Galapagos finches, initially observed by Charles Darwin.
Section 3.0 What is the Significance of Biodiversity?
Task 7: Read the excerpt below and use the interactive slider.
Once biodiversity is established in an area, there are heavy consequences for its collapse. The greatest example of this is with the removal or eradication of keystone species. These organisms are foundational species for an area, meaning their presence keeps the living systems surrounding them regulated. When removed, the ecosystem shortly collapses. One example is the sea otter! As illustrated in the image to the left, when sea otters are present in their environment, barnacle populations remain at low sustainable levels, allowing lush kelp forests to grow and provide shelter for a wide array of aquatic biodiversity. When sea otters are removed from their environment, barnacle populations grow exponentially without predation, resulting in a reduction of kelp forests. Once home to many fish species, without kelp these organisms must find new homes, and as a result are either forced to leave the area or are exposed to predators and collapse themselves.
Non-keystone species also have ecological roles in their environment, which can cause domino effects for species that rely on interactions with them or something they were directly involved with. For instance, some caterpillars are known to take place in what is known as ecosystem engineering. This means the organisms are altering their environment in some way, which in turn can be useful for other creatures. In the case of caterpillars, many will create sheltered burrows in rolled-up leaf material. These burrows remain once the caterpillar no longer needs them, and is then used as a home for many different types of insects.
Regardless of ecological status, all species comprising our global biodiversity contain intrinsic value for their representation of millions of years of evolutionary lineages and evolutionary potential.
Use the slider below see a real-world example of an ocean ecosystem before and after the removal of the keystone species
Leftmost, Outermost Photo Credit to University of California, Santa Barbara | Innermost Photo (Both Panels) Credit to BISHOPAPPS via The Ohio State University.
Task 8: [Updating, Apologies for Inconvenience] Future Task Objectives: revisit the keystone species example of the otter from the perspective of it being a crucial component to kelp production/CO2 sequestration; introduce the role of keystone pollinator species in crop viability and production/global nutrition value.
Task 9: Read the brief paragraph below, then follow the link to the hhmi BioInteractive module Interactive Exploration of Coral Bleaching.
The total area of Earth consists of 29% water coverage and 71% land spread1. Nearly 1/3 of the planet, unexplored at the depths, is home to 80% of known life2. These organisms can be quite different in appearance, but are united under a common threat: climatic consequences threatening their aquatic habitats. One particularly biodiverse ecosystem type under threat are coral reef systems.
1 USGS. 2019. Water Science School. Access Here
2 National Geographic. 2023, One Ocean, Chapter Three. Access Here
As ocean bodies are exposed to higher carbon dioxide (CO2) levels, the pH of the water shifts toward the direction of 0 on the scale, leaning more acidic with further CO2 accumulation. This is demonstrated visually in the diagram below.
With few exceptions, marine species require a [update in progress, Apologies for the inconvenience]
Explore the effects of rising temperatures on ocean acidification, and the effects on biodiversity within the reefs in the interactive module linked below.
Interactive Exploration of Coral Bleaching
Hosted by hhmi BioInteractive (13+)
Compassion Crossing 