1. Ecology
Lesson 9.2

2. Lesson Objectives
• Identify the factors that define terrestrial biomes.
• Identify and describe the different terrestrial biomes found
on Earth.
• Determine how climate affects terrestrial biomes.
• Give an overview of aquatic biomes.
• Identify the factors that define aquatic biomes.
• Identify and describe the different aquatic biomes found on
Earth.
• Determine how climate affects aquatic biomes.

3. Terrestrial Biomes
Terrestrial biomes include all the land areas on Earth where organisms live. The distinguishing features of terrestrial biomes are determined mainly by climate (abiotic factor). Terrestrial biomes include tundras, temperate forests and grasslands, chaparral, temperate and tropical deserts, and tropical forests and grasslands.

4. Survey of Terrestrial Biomes
Terrestrial biomes are classified by climatic factors and types of primary producers.

5. Terrestrial Biomes and Climate
Climate is the average weather in an area over a long period of time. Weather refers to the conditions of the atmosphere from day to day.
In terms of moisture, climates can be classified as arid (dry), semi-arid, humid (wet), or semi-humid. The amount of moisture depends on both precipitation and evaporation.
Biomes are categorized based upon their climate types.

6. Climate and Biodiversity
Climate determines plant growth, it also influences the number and variety of other organisms in a terrestrial biome. Biodiversity generally increases from the poles to the equator. It is also usually greater in more humid climates.

7. Climate and Adaptations
Organisms evolve adaptations that help them survive in the climate of the biome where they live. For example, in biomes with arid climates, plants may have special tissues for storing water. The desert animals also have adaptations for a dry climate. In biomes with cold climates, plants may adapt by becoming dormant during the coldest part of the year. Dormancy is a state in which a plant slows down cellular activities and may shed its leaves. Animals also adapt to cold temperatures. One way is with insulation in the form of fur and fat.

8. Aquatic Biomes
Terrestrial organisms are generally limited by temperature and moisture. Therefore, terrestrial biomes are defined in terms of these abiotic factors. Most aquatic organisms do not have to deal with extremes of temperature or moisture. Instead, their main limiting factors are the availability of sunlight and the concentration of dissolved oxygen and nutrients in the water.

9. Types of Aquatic Biomes
Freshwater Regions
Low Salt content Ponds and Lakes
Streams and Rivers bodies of flowing water moving in one direction
Wetlands areas of standing water that support aquatic plants

10. Ponds and Lakes
Many ponds seasonal; lakes may exist for hundreds of years or more
Both have limited species diversity since they are often isolated from one another and from other water sources
Divided into three different “zones”; determined by depth and distance from the shoreline
topmost zone near the shore of a lake or pond is the littoral zone
The near-surface open water surrounded by the littoral zone is the limnetic zone
deep-water part of the lake/pond, the profundal zone
The topmost zone near the shore of a lake or pond is the littoral zone. This zone is the warmest since it is shallow and can absorb more of the Sun’s heat. It sustains a fairly diverse community, which can include several species of algae (like diatoms), rooted and floating aquatic plants, grazing snails, clams, insects, crustaceans, fishes, and amphibians. In the case of the insects, such as dragonflies and midges, only the egg and larvae stages are found in this zone. The vegetation and animals living in the littoral zone are food for other creatures such as turtles, snakes, and ducks.
The near-surface open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. Plankton are small organisms that play a crucial role in the food chain. Without aquatic plankton, there would be few living organisms in the world, and certainly no humans. A variety of freshwater fish also occupy this zone.
Plankton have short life spans—when they die, they fall into the deep-water part of the lake/pond, the profundal zone. This zone is much colder and denser than the other two. Little light penetrates all the way through the limnetic zone into the profundal zone. The fauna are heterotrophs, meaning that they eat dead organisms and use oxygen for cellular respiration.
Temperature varies in ponds and lakes seasonally. During the summer, the temperature can range from 4° C near the bottom to 22° C at the top. During the winter, the temperature at the bottom can be 4° C while the top is 0° C (ice). In between the two layers, there is a narrow zone called the thermocline where the temperature of the water changes rapidly. During the spring and fall seasons, there is a mixing of the top and bottom layers, usually due to winds, which results in a uniform water temperature of around 4° C. This mixing also circulates oxygen throughout the lake. Of course there are many lakes and ponds that do not freeze during the winter, thus the top layer would be a little warmer.

11. Streams and Rivers
Found everywhere—they get their starts at headwaters, which may be springs, snowmelt or even lakes, and then travel all the way to their mouths, usually another water channel or the ocean
These are bodies of flowing water moving in one direction. Streams and rivers can be found everywhere—they get their starts at headwaters, which may be springs, snowmelt or even lakes, and then travel all the way to their mouths, usually another water channel or the ocean. The characteristics of a river or stream change during the journey from the source to the mouth. The temperature is cooler at the source than it is at the mouth. The water is also clearer, has higher oxygen levels, and freshwater fish such as trout and heterotrophs can be found there. Towards the middle part of the stream/river, the width increases, as does species diversity—numerous aquatic green plants and algae can be found. Toward the mouth of the river/stream, the water becomes murky from all the sediments that it has picked up upstream, decreasing the amount of light that can penetrate through the water. Since there is less light, there is less diversity of flora, and because of the lower oxygen levels, fish that require less oxygen, such as catfish and carp, can be found.

12. Wetlands Marshes, swamps, and bogs are all considered wetlands
Plant species adapted to the very moist and humid conditions are called hydrophytes.
include pond lilies, cattails, sedges, tamarack, and black spruce.
Marsh flora also include such species as cypress and gum.
Wetlands have the highest species diversity of all ecosystems.
Wetlands are areas of standing water that support aquatic plants. Marshes, swamps, and bogs are all considered wetlands. Plant species adapted to the very moist and humid conditions are called hydrophytes. These include pond lilies, cattails, sedges, tamarack, and black spruce. Marsh flora also include such species as cypress and gum. Wetlands have the highest species diversity of all ecosystems. Many species of amphibians, reptiles, birds (such as ducks and waders), and furbearers can be found in the wetlands. Wetlands are not considered freshwater ecosystems as there are some, such as salt marshes, that have high salt concentrations—these support different species of animals, such as shrimp, shellfish, and various grasses.

13. Marine Biomes
Marine regions cover about three-fourths of the Earth’s surface
Oceans
Coral reefs
Estuaries
Marine algae supply much of the world’s oxygen supply and take in a huge amount of atmospheric carbon dioxide
Evaporation of the seawater provides rainwater for the land.

14. Oceans Largest of all the ecosystems; high salt content Four zones:
Intertidal where ocean meets land
Pelagic  areas furthest from land; open ocean
Abyssal  deep ocean
Benthic  area below pelagic zone
Great diversity of species
The largest of all the ecosystems, oceans are very large bodies of water that dominate the Earth’s surface. Like ponds and lakes, the ocean regions are separated into separate zones: intertidal, pelagic, abyssal, and benthic. All four zones have a great diversity of species. Some say that the ocean contains the richest diversity of species even though it contains fewer species than there are on land. The intertidal zone is where the ocean meets the land—sometimes it is submerged and at other times exposed, as waves and tides come in and out. Because of this, the communities are constantly changing. On rocky coasts, the zone is stratified vertically. Where only the highest tides reach, there are only a few species of algae and mollusks. In those areas usually submerged during high tide, there is a more diverse array of algae and small animals, such as herbivorous snails, crabs, sea stars, and small fishes. At the bottom of the intertidal zone, which is only exposed during the lowest tides, many invertebrates, fishes, and seaweed can be found. The intertidal zone on sandier shores is not as stratified as in the rocky areas. Waves keep mud and sand constantly moving, thus very few algae and plants can establish themselves—the fauna include worms, clams, predatory crustaceans, crabs, and shorebirds.
The pelagic zone includes those waters further from the land, basically the open ocean. The pelagic zone is generally cold though it is hard to give a general temperature range since, just like ponds and lakes, there is thermal stratification with a constant mixing of warm and cold ocean currents. The flora in the pelagic zone include surface seaweeds. The fauna include many species of fish and some mammals, such as whales and dolphins. Many feed on the abundant plankton.
The benthic zone is the area below the pelagic zone, but does not include the very deepest parts of the ocean (see abyssal zone below). The bottom of the zone consists of sand, slit, and/or dead organisms. Here temperature decreases as depth increases toward the abyssal zone, since light cannot penetrate through the deeper water. Flora are represented primarily by seaweed while the fauna, since it is very nutrient-rich, include all sorts of bacteria, fungi, sponges, sea anemones, worms, sea stars, and fishes.
The deep ocean is the abyssal zone. The water in this region is very cold (around 3° C), highly pressured, high in oxygen content, but low in nutritional content. The abyssal zone supports many species of invertebrates and fishes. Mid-ocean ridges (spreading zones between tectonic plates), often with hydrothermal vents, are found in the abyssal zones along the ocean floors. Chemosynthetic bacteria thrive near these vents because of the large amounts of hydrogen sulfide and other minerals they emit. These bacteria are thus the start of the food web as they are eaten by invertebrates and fishes.

15. Coral Reefs Widely distributed in warm shallow waters
barriers along continents (e.g., the Great Barrier Reef off Australia), fringing islands, and atolls
dominant organisms in coral reefs are corals
consist of both algae (zooanthellae) and tissues of animal polyp
other species: microorganisms, invertebrates, fishes, sea urchins, octopuses, and sea stars
reef waters tend to be nutritionally poor, corals obtain nutrients through the algae via photosynthesis and consumption of plankton

16. Estuaries
Areas where freshwater streams or rivers merge with the ocean
mixing of waters with different salt concentrations creates a very interesting and unique ecosystem
Microflora like algae, and macroflora, such as seaweeds, marsh grasses, and tropical mangrove trees
Diverse fauna, including a variety of worms, oysters, crabs, and waterfowl

17. Aquatic Biomes and Sunlight
In large bodies of standing water, including the ocean and lakes, the water can be divided into zones based on the amount of sunlight it receives:
1. The photic zone extends to a maximum depth of 200 meters; enough sunlight penetrates for algae and other photosynthetic organisms to photosynthesize.
2. The aphotic zone is water deeper than 200 meters; too little sunlight penetrates for photosynthesis to occur. As a result, food must be made by chemosynthesis or else drift down from the water above.

18. Aquatic Organisms
Aquatic organisms generally fall into three broad groups: plankton, nekton, and benthos. They vary in how they move and where they live.
1. Plankton are tiny aquatic organisms that cannot move on their own. They live in the photic zone. They include phytoplankton and zooplankton. Phytoplankton are bacteria and algae that use sunlight to make food. Zooplankton are tiny animals that feed on phytoplankton.
2. Nekton are aquatic animals that can move on their own by ‘‘swimming” through the water. They may live in the photic or aphotic zone. They feed on plankton or other nekton. Examples of nekton include fish and shrimp.
3. Benthos are aquatic organisms that crawl in sediments at the bottom of a body of water. Many are decomposers. Benthos include sponges, clams, and anglerfish which are adapted to a life in the dark.

19. Lesson Summary
Describe characteristics of biotic and abiotic components of aquatic and terrestrial ecosystems
Terrestrial biomes are determined mainly by climate. Climate influences plant growth, biodiversity, and adaptations of land organisms. Terrestrial biomes include tundras, temperate forests and grasslands, chaparral, temperate and tropical deserts, and tropical forests and grasslands.
Aquatic biomes are determined mainly by sunlight and concentrations of dissolved oxygen and nutrients in the water. Aquatic organisms are plankton, nekton, or benthos.