02.04 Adaptation and Succession Assignment

02.04 Adaptation and Succession

Adaptation and Succession

Breeders and farmers are aware that different animals in a species have different features. Some plants will grow larger fruit than average, and some cows will provide more milk than average. By selecting breeding animals with a desirable trait and then deliberately crossing selected breeding animals, the breeders can change a species over many generations. This is known as artificial selection. If a species can change over a few generations through deliberate human selection, then with the natural selection of advantageous traits, a species should be able to change over hundreds or thousands of generations.

Lesson Focus

The terms adaptation and natural selection are sometimes mistakenly used interchangeably. Ask students to consider what they are already familiar with about this lesson’s focus with these questions:

Suppose you never left the region of the equator during your life, and your cousins asked you to visit them for one year in Alaska. What kind of adoptions would you make for the variation in climate? Explain how life forms have naturally adapted in Alaska.
Today’s breeds of dogs are thought to have been independently domesticated from wild dogs. What other uses might artificial selection have for man?

When farmers choose a plant or animal with the characteristics they prefer to pass on to the next generation, they are using artificial selection, but nature has been responsible for ecosystems changing over time.

Enduring Understanding

Ecosystems are structured and diverse and change over time.

Learning Objectives

Define in what way organisms adapt to their environment.
Describe ecological succession.
Describe the effect of ecological succession on ecosystems.

Essential Knowledge

Organisms gradually adapt to their environments over both short- and long-term periods through incremental genetic changes.
Environmental changes (sudden or gradual) may pose a threat to the survival of a species, and individuals must change their behaviors, migrate, or die.
Ecological succession is divided into two types, i.e., primary and secondary.
The species with activity particularly important to the community structure in an ecosystem is called a keystone species.
Indicator Species: Any species characteristic of an ecosystem that, by its presence, abundance, scarcity, or chemical makeup, shows that a particular aspect of the character or quality of that ecosystem is present.
Pioneer members of an early successional species are often the first to enter into unoccupied habitat and over time may become optimised to its special conditions, leading to the development of new species.
The total biomass, species richness, and net productivity of a disturbed ecosystem will change over time as succession occurs.

Evolution

Public Domain

When there are no witnesses present in a crime, detectives search for numerous kinds of evidence that may aid them in solving the puzzle and figuring out what exactly transpired. Similarly, fossils, DNA sequences, structural similarities, and other types of evidence are used to explain past events, the relationships of organisms on Earth, and the origins of the diversity of life on Earth today.

In this way, scientists construct and strengthen the theory of the origin of life on Earth. The current scientific views about evolution did not develop overnight. It is important to remember that, like any scientific theory, the theory of evolution has been based on observations, scientific analysis, and evidence from a wide variety of scientists in many different fields.

In science, a change in the genetic material (allele frequencies) of a population over time is called evolution. This change in a population is an example of the transformation of life on Earth from its early forms to the tremendous diversity on Earth today. These changes occur mainly because of the interactions between the populations of organisms and their habitats.

Charles Darwin’s contributions to that theory were important, and his interpretations of the evidence were his own. Darwin documented his observations of organisms in an assortment of environments on the continents of South America, Australia, and Africa. Three patterns of biological diversity were observed by Darwin on his journeys: variation of species around the world, locally, and with the passage of time.

Species vary globally

Darwin noticed that comparable ecosystems in different parts of the world have some similar, but unique, organisms. For instance, he discovered among the grasslands of Australia, Africa, and South America, large flightless birds.

2011 Public Domain/John Foxx/Tom Brakefield/Thinkstock

While all of these birds have similarities, they are all large and flightless; they have other differences too, and do not seem to have had a close common ancestor.

Species are not necessarily found in the same ecosystems around the world. Rabbits do well in the grasslands of Europe, but don’t belong in the grasslands of Australia or Africa. Kangaroos are endemic to the grasslands of Australia – that is, they do not occur on other continents. How did the continents differ in their species?

Species vary locally

Public Domain

The most apparent change between the thirteen finch species on the Galapagos Islands is in their various beak shapes that are adapted to the type of food each species can eat.

Darwin also noticed that different regions of an area or continent were inhabited by unique species that were closely related to each other. For instance, the Galápagos Islands comprise a chain of islands situated off the Pacific coast of South America. Although they are in close proximity, each of these islands has a unique ecosystem. As if the plants and animals of the South American mainland were living on these islands, yet the species had been modified so that they were unique to each island. Darwin collected 13 kinds of finches in the Galapagos Islands.

While they were similar in many respects, each of these finches was from a population that had enough unique characteristics to warrant their classification as a separate species. Some types of finches were only found on one island, while others could be found on two or three islands that were close together. Large tortoises were also present on several of the islands and were superficially similar, but had different shell shapes that are characteristic of each island.

Species vary over time

Fossils of extinct species were also collected by Darwin on his voyage. Some of these fossils were like living things, others were not. For example, Darwin unearthed a fossil of the extinct armored animal called the glyptodont. A smaller armadillo, also found in this area, was more like this ancient creature. Darwin knew that the glyptodont had to be an ancestor of the modern-day armadillo.

Natural Selection

Changes over time in populations, and consequently communities, are also the result of evolution. Evolution can have two main outcomes:

New species develop over time.
New species evolve through modification of preexisting ones to adapt to a new environment.

The idea that evolution is responsible for the diversity of life on Earth is not new, but is rather the suggestion of Charles Darwin. He did, however, propose a mechanism by which evolution operated – one of natural selection. The organisms that are best adapted are more likely to survive, and the organisms with the maladaptive traits are less likely to survive. Natural selection is in response to biotic and abiotic aspects of an ecosystem. Due to these complex influences, evolution has a strong effect on the organization of niches for organisms.

There are many examples of coevolution in many species. A population of beetles, for instance, could be a parasite of a population of maple trees. The maple trees may develop their ability to produce a natural insecticide, which kills the beetles in some of the maple trees. Beetles that are more resistant to the insecticide are more likely to survive. Over time, most of the beetle population will be resistant to the pesticide. The more insecticide trees produce, the more they will survive as the pesticide resistance in the beetles increases. Thus, the traits of one beetle population impact the traits of the maple tree population, and the traits of the maple tree population impact the traits of the beetle population.

Community Ecology Text Version

Zion National Park

The Zion National Park is the result of the downcutting of a river, which has cut down the rocks vertically. The downcutting in Zion Canyon was attributed to the Virgin River, which has formed steep walls around the canyon. The steep walls and the river form geographical boundaries for many species, allowing them to become isolated. Organisms that live in the desert swamp, such as the leopard frog and tree frog, are adapted for life in and near the water.

Crystal Springs Preserve

The property has a large spring that bubbles up through fractures in the limestone of Crystal Springs Preserve. Only those species that are capable of surviving on wet ground, like frogs, or where it is drier, like trees, can survive in this area.

Yellowstone

The Rocky Mountains form the side of Yellowstone, which is located on a high plateau of 8,000 ft. Many of the vast high plateaus are calderas, a bowl-like depression that results from the collapse of the magma chamber under a volcano, which causes rock above it to subside. Below the caldera, the hot rock and magma continue to cause the mud pots and geysers, for which Yellowstone is so well known. But there are also high alpine meadows in Yellowstone that have no geothermal features. Organisms inhabiting geothermal regions must be adapted to withstand extreme temperatures, while those living in high alpine meadows must endure severe winter conditions. Bears hibernate, white pelicans migrate southward, and elk and bison grow thick winter coats and move to lower elevations.

So why is it that there are comparable organisms living in the desert swamp at Zion National Park, and also at the spring at the Crystal Springs Preserve? There is a similarity in the niche of these organisms in a similar environment. So why are the organisms at the two parks, Zion National Park and Yellowstone National Park, different? They are functioning in different niches in environments affected by different abiotic factors.

Natural selection is a mechanism that accounts for how a population can become more adapted to its local environment over many generations. The main principles of natural selection include variation, overpopulation, adaptation, and descent with modification.

Changing Environments

Populations change from generation to generation, as they become better adapted to the environment. Natural selection is not in a predictable direction. The environment may change, and some traits, once beneficial adaptations, may no longer be useful. Such environmental changes may include climate change, the introduction of new plant or animal species, pollution, and other forms of human impact. Such changes can result in new traits being the adaptations that enable survival in the new environment. Otherwise, the species might face extinction if environmental change takes place faster than the speed of their adaptation to environmental change.

Examples

Let’s examine some examples of natural selection. In each example, see how natural selection acts on individuals in a population, enabling those individuals with the favourable adaptations to survive and reproduce more frequently than others. Be sure to pay attention to how changing the environment may alter the characteristics that are advantageous for the organisms.

Rat Snakes

Rat snakes are common in North America, with numerous populations. All rat snakes have a similar diet and kill their prey by constriction, and they are all excellent climbers. But rat snakes vary in coloration, ranging from black to yellow-striped, orange, or green. Different populations exhibit distinct dominant color variations depending on the regions they inhabit. This is because each population has adapted with natural selection over time, and some individuals have developed a colour that is most effective in that habitat. Those who blend in most successfully can hide best from any predators and prey and thus pass on the genes for that adaptive colouration.

Antibiotic-resistant Bacteria

Antibiotics are used to fight bacterial infections. If the number of bacteria is large, the population will contain bacteria with different genetic traits, which are a result of mutations resulting from DNA replication. Most bacteria of a population will die rapidly when exposed to antibiotics. But in the large group of single-celled bacteria, some people may be able to survive the exposure to the medicine because they have mutations.

The remainder of the bacteria multiply quickly, creating the next generation within a short period of time. Most of the organisms of the new population will have that characteristic that enabled the “parent cells” to withstand the antibiotic. If sufficient time is allowed and several exposures to the same antibiotic are given to a population of bacteria, antibiotic resistance can develop. A bacterium, methicillin-resistant Staphylococcus aureus or MRSA, is sometimes referred to as a “superbug” as it is no longer susceptible to many antibiotics. Bacteria continue to build up resistance to antibiotics, and we are not finding alternatives to fight the diseases caused by bacteria.

Peppered Moths

One famous example of natural selection is the peppered moth from Great Britain and Ireland (Biston betularia). Throughout the English Midlands, two main varieties, differing in colouration, are found. Both varieties are light with dark spots and dark uniform. Both moths are nocturnal, and both species spend the day concealed on trees or rocks that are underlain with light-colored lichens. The light coloured moths blended in more with this background, and the dark moths were picked out and consumed by birds. In pre-industrial days, the dark moths were very rare as most of them failed to survive long enough to breed and pass on the dark colouring genes.

In the late 1800s, the countryside’s landscape was made darker by industrial pollution, making the light moths more conspicuous. Gradually, the number of dark moths in the population began to rise, and light moths declined, since this dark coloring would now be an advantage in this new habitat. By the end of the century, almost all the peppered moths in the Manchester area were dark. As the countryside became less polluted, lighter moths began to increase after the peak of the Industrial Revolution.

Galapagos Finches

The image shows a graph of the patterns of natural selection in Galapagos finches. Beak size is plotted on the y-axis, while the years are represented on the x-axis. The beak size is 9.9 mm, and 1978 was a dry year. In 1980, it was a dry year, and the beak on average was approximately 9.7 millimeters in size. This beak size is measured for the year 1982, which was also a dry year.

The 13 types of finches found in the Galapagos Islands share some similarities, but each population has its own unique traits, as well. The main difference between the groups is the shape of their beaks, which is suited to the particular diet on which they feed. Some beaks are adapted for eating seeds or berries, others for probing with sticks to search for food, and others for searching for insects or grubs.

In one finch species, the medium ground finch (Geospiza fortis), they have a very hard beak, which they use to crush the seeds. Mainly feed on small seeds produced in abundance in years of high rainfall. During dry years when these seeds are scarce, those finches have been seen eating larger, tougher seeds. Beak shape and size vary within a population. During prolonged droughts, medium ground finches with larger beaks are better able to crack large seeds than those with smaller beaks. Thus, during a drought, large beaked finches will be more “fit” than small beaked finches; large beaked finches will survive and be able to reproduce more frequently. In years in which there is a large amount of precipitation, greater numbers of the birds with smaller beaks survive and are able to raise young.

Let’s take another example. What environment do you imagine penguins would live in?

If you weren’t, you would be! Penguin habitats include all around the Southern Hemisphere, and the Galapagos Penguin lives on the equatorial Galapagos Islands in an average temperature of 73°F. It’s true! Penguins are one of many examples of the diversity of life; there are many different species. Penguins themselves are a pretty strange bird to begin with, calling their wings into use to skim across the water rather than the air, but the Galapagos penguin is even weirder.

The Galapagos penguin (Spheniscus mendiculus) has some interesting physical adaptations to survive in the sun, heat, and changing food sources. The cool waters of the Humboldt and Cromwell currents offer relief during the day, yet Galápagos penguins still require ways to protect themselves from the intense equatorial sun. Are unable to sweat, but like dogs, they can pant. This is because these penguins are also less fatty and have fewer feathers compared to penguins living in colder climates. Galapagos penguins are one of the smallest species of penguins, and can survive on fewer calories when food is scarce.

Life can be tough in the sea, particularly if one isn’t one of the biggest killers. How do adaptations help an organism survive? Let’s examine some of the special adaptations of ocean life:

How do marine mammals keep from freezing to death in Arctic waters?

Fur or blubber! The dense hairs contain a layer of air close to the skin for insulation. Whenever animals live most of the time in water, they use blubber, which is a layer of tissue composed of fat, collagen, and elastin. Just like fat, blubber insulates and stores energy for marine mammals.

Can whales really hold their breath for more than 90 minutes?

Yes! Whales, air-breathing mammals. Myoglobin is an oxygen-binding protein found in the muscles of whales, as well as other diving animals, and whales can store more oxygen to burn while they are diving.

How is energy generated at the bottom of the ocean, where sunlight cannot reach?

How does energy get generated at the bottom of the ocean when there isn’t any sunlight?

Most forms of producers, such as plants and algae, use the sun as an energy source. In the deep ocean, however, where there is no sunlight, venting of fluids happens at hydrothermal vents, which spew superheated fluids laced with chemicals from the ocean floor. Microorganisms adapted to these extreme conditions have been dubbed ‘hyperthermophiles’ and are able to reproduce and grow at temperatures of 90°C or higher.

Ecological Succession

Successions may drastically alter the composition and development of whole communities, occurring on a large scale. As you’ve seen, communities do not remain the same over time. When they reach their carrying capacity (the average of the maximum and minimum of the population), they “succession” into communities that differ from pioneer communities to climax communities to best utilize available resources, such as sun, water, and nutrients.

The characteristics of pioneer communities can be compared to the characteristics of climax communities in the table below:

Secondary Succession Effect on Ecosystems

The first of these, primary succession, is the progression of growth that develops on newly- formed land or surfaces. It is not possible to have primary succession without bare rock. For example, on the Island of Hawaii, active volcanoes are a component of the island ecosystem. The youngest of the volcanoes, Kilauea, produces 250,000–650,000 cubic yards (200,000–500,000 cubic meters) of lava per day. As soil accumulates over this lava, it forms into new rock, then into new land. Lichens affix themselves to the rock in the pioneer community. The lichens help to fracture the rock (physical weathering). Moreover, their cells secrete acids that dissolve some of the minerals in the rock (chemical weathering). Lichens consist of fungi growing in association with photosynthetic algae; the fungi protect and provide additional nutrients for the algae while the algae provide food for the fungi.

The lichens thrive in the most inhospitable habitats due to this helpful association and relationship. The lichens dissolve the rocks and create thin soil. As time passes, mosses can start to grow within the soil; eventually, the Mosses may be able to replace the Lichens. The seeds are carried by the wind or spread by the birds into the new soil and start to grow. The community can develop into grasses and then shrubs, with the deepening of the soil, and eventually small and then large trees in a forest. They are responsible for the increase of vegetation and thus contribute to the attraction of herbivores and omnivores. The new land acts as a new habitat and provides for the ecosystem and population growth.

Primary Succession Text Version

Animation showing the progression in primary succession from rocks to lichens and mosses to grasses to shrubs to small trees to large trees.

Check your understanding on adaption with this interactive. The answer is: artificial selection.

The answer is: fitness.

The answer is: Adaptation.

The answer is: variation, overpopulation, and inheritance.

The answer is: Adaptations are specific to the current environment, and may no longer be beneficial if the environment changes.

Assessment

During this lesson, you learned about the way that ecosystems change over time by adapting and succession. Natural selection is one way of evolution. Variations in traits already exist in a population of organisms, and some of these are more advantageous in a particular environment than others. Primary and secondary succession, pioneer and climax communities have been discussed. You also looked at the important role keystone species and indicator species have in a community. Finally, you explored how succession would impact the biomass, species richness, and net productivity in a disturbed ecosystem through time.

Natural Selection Activity

Predation is a significant force of evolution. The prey with beneficial adaptations that enable it to survive longer or outsmart the predator will stay alive, transferring this adaptation to many or all of its offspring. Over time, this natural selection can lead to an increase or decrease of a trait in a population. However, how do those attributes affect the survival of the population as a result of other events?

Complete the Natural Selection Worksheet as you play through the simulations. Consider reviewing the Graphing Tutorial in the Toolkit for the data analysis section of the lab report. Please read the grading rubric before submitting for a grade.

Natural Selection

Introduction:

This activity will investigate the scientific theory of evolution by examining the number of a species that survives when an environment changes.

Natural Selection Activity Rubric

The report will provide an estimate of the time needed to adapt and succeed.

Check your understanding of important concepts.
Fill in the Natural Selection Worksheet.
Turn in the 02.04 Adaptation and Succession activity.