ADAPTATION TO HABITATS Lecture Objectives 1. Define ecology and the related terms discussed. 2. Build a simple food web using only insects for the primary, secondary and tertiary trophic levels. 3. Describe the ways insects have adapted to the soil and aquatic environments. 4. Discuss the advantages of biological monitoring and the specific indications of poor water quality. 1 2 Introduction Terms and Concepts Ecology - The study of the interactions between organisms and their environment. Are you ready for an adventure? We are now going to take a journey to some specialized habitats where insects have become very successful. In unit Environment - The environment is the physical world that affects the life of an 3, you learned of some of the adaptations such as gills for breathing underwater, individual, population or community. It is composed of two parts, the Biotic which and in lab you learned of various leg adaptations for digging in soil. Now we are includes all living organisms such as plants, animals and microbes, and the Abiotic going to explore some of the specific habitats where these adaptations, and others, or non-living factors such as temperature, light, water, and nutrients. are useful. Before we begin the lecture, please read the text chapter on aquatic insects, pages 240-251, and 260 and the chapter on soil insects pages 216-230 Habitat: A habitat is the locality or site and type of environment that an organism and 233. lives on or in. A pond, field or oak tree are all examples of habitats. Niche: A niche is the ecological role a species plays in a community such as an insect that feeds on root of grasses or one that eats aphids on leaves. It is what an organism does for a living within a habitat. Population: A population is a group of individual organisms that belong to the same species and live in a particular geographic location. Community: A community is all the organisms living in a particular area and includes populations of different species of plants and animals. 3 Ecosystem: An ecosystem is the combination of the community of organisms in 4an Read textbook pages 240-251, and 260, and 216-230 and 233. area and the abiotic factors such as the air, water and soil. Biological Monitoring Water Quality Traditionally, water quality has been tested in the laboratory by measuring the One important way insects are being used by humans is to determine the relative chemicals found in the water. This method is popular because it is quick and health or level of pollution in aquatic habitats. This is done by sampling the insects easy to do. One problem with these kinds of tests though, is that the in a lake or stream and measuring the number of individual insects, and most sample may be taken on a day when the factory or pollution source is not releasing any chemicals so none will show up on the tests. Another is the importantly, the number of species. The results are then compared with those from difficultly knowing which chemicals to test for or what effect the interaction of the samples taken in other lakes or different portions of the stream. different chemicals present may have on living organisms. Biological monitoring has an advantage over chemical tests because you can collect the sample at any Some insects are very hardy and will be found in almost any quality of water time and still get a reliable water quality reading. This is because the insects are samples. Others, however, are much more sensitive and are found only in constantly sampling the water over long periods of time. unpolluted water. A healthy lake or stream will have a wide variety of species (including those sensitive to pollution) while a polluted stream will have only a few If you take a sample on a day when the factory or pollution source is not hardy species though they may be present in large numbers . If you find very few releasing chemicals, the insects you will find in the water will not be different than the insects you would find on a day the factory was not releasing chemicals. sensitive species and many pollution tolerant species, that usually means there is When taking water samples for water quality tests, you usually take a sample pollution in the water. above the factory, or other potential pollution source, and one below the factory . You then compare the results. If you have a lot of sensitive species at sample site 1, and very few at Sample site 2, then the source of pollution may be the factory. However, if you found the same numbers of species at both sites 1 and 2 then you would assume the factory is not contributing significant amounts of pollution. 5 6 1 Water Quality Indicators Aquatic Habitats There are different kinds of aquatic habitats, and with each habitat comes different insect fauna and different functional feeding groups. The aquatic habitats we will discuss include: •Lentic (ponds and lakes) - standing water •Lotic (streams and rivers) - running water •Marine (inter-tidal and littoral) •Temporary bodies of water – puddles, crab-holes, tree holes Important factors when considering aquatic habitats include: water When sampling there are several common indicators to consider. speed, water temperature, and dissolved solvents. •Mayflies indicate an increase in particulate matter. •Bloodworms (Chironomidae) increase when oxygen levels drop. •Plecoptera decline as water temperature increases. •Many species disappear with pesticide run-off. •There will be an abundance of only a few species with eutrophication (abundance of organic matter). 7 8 Functional Feeding Groups Insects and the Aquatic Environment Shredders - feed on living or decomposing plant tissues, including wood which they chew, mine or gouge. (water boatman) Collectors - feed on fine particulate matter by filtering particles from aqueous suspension. (black fly larvae) Scrapers - feed on attached algae and diatoms by grazing solid surfaces. (dytiscid water beetles) Piercers - feed on cell and tissue fluids from vascular plants of larger algae by piercing the cell wall and sucking out the contents. Predators - feed on living animal tissue. (Helgrammites, Megaloptera,-only found in clean waters.) Parasites - feed on living animal tissue as external or internal parasites of Take a close look at the drawing of the stream in front of you. Below the stream any stage of another organism. are enlarged pictures of insects with lines indicating where they would be found in the stream. Think about where in the stream the different insects are located. Is Scavengers – feed on dead plant or animal materials (detritus). (water the water moving fast or slow, is it deep or shallow, is it rocky or muddy? On the next few slides we will discuss the location of these insects in the aquatic habitat. striders) See if you can fit the examples from the following diagram to their correct functional feeding groups. 9 You may want to refer back to this diagram from time to time. 10 Aquatic insects Aquatic Insects - continued Look now at the damselfly. This insect represents predacious aquatic insects that sit Lets start with the mosquito larvae at the left side of drawing on the quietly and grab prey when it swims by. It also represents insects that have developed previous slide. Notice that it is found in the quiet part of stream and that it gills (the leaf-like tail structures) to help them breath underwater. They use their gills is near the surface of the water. This mosquito larvae represents a number for cutaneous gas exchange. of insects that hang from the surface tension of the water as though they were hanging from the ceiling. They do this so that they can remain near Next is the water strider. The water strider represents those insects that live on the the surface and breath through their snorkel-like tail that has a spiracle water surface supported by the surface tension. These insects also have hydrofuge opening in the end. They hang from the surface using a special ring of structures, in this case their long legs and tarsi. Water striders (Gerridae) are also hairs that surround spiracle. These hairs extend out over the surface of the scavengers of dead and dying insects that fall on the water surface. water like grappling hooks. The hairs, spiracle opening, and trachea are all hydrofuge structures. This means that they are water repellant. Water boatmen represent those insects that are simply good swimmers. They graze on aquatic plants near the bottom of the stream or pond. The water boatman also represents those insects that carry air with them from the surface. This air can either be carried as film or bubble, plastron, on the outside of the body or between the wings and abdomen. As the oxygen is sucked out of the bubble of air the ratio of nitrogen in the bubble in increases causing the bubble to absorb oxygen from the water. This gas exchange increases the amount of time the insect can stay underwater. crabhole mosquito larvae 11 12 Hemiptera: Corixidae (water boatman) 2 Aquatic Insects - continued Video – Brine Flies The mayfly larvae illustrated in the diagram is a type that burrows in the mud at the bottom of lakes and slow moving streams and rivers. They eat small food particles that float past in the water. The caddisfly larvae illustrated is one that builds a case or home for itself out of rocks or other debris. It feeds by grazing on the algae or other plant matter on the bottom of the water. Other caddisfly larvae actually spin a web between rocks on the stream bottom in which they catch small food particles.