Thursday, May 18, 2017

Paired Reading Passages 4th Grade | What is Expository Text?

Paired Reading Passages | Free Paired Informational, Nonfiction, Expository Reading Text | What is an Expository Text? Facts, Arguments, Claims, Statements, Cause and Effect, and Even Opinion. 

Expository Reading: Perspective, Attitude
  • Analyzes these paired informational texts for evidence of bias or stereotypes 
  • Determines author's attitude or perspective in the paired of informational text 
  • Determines the difference in focus of two informational texts on the same or similar topic 
  • Evaluates author's attitude in informational text to make an inference
Coral Reef Systems: The Great Barrier Reef
The world’s biggest coral reef system is The Great Barrier Reef which is located off the sea coast of Queensland in the Coral Sea, in Australia. It consists of 900 islands that extend for more than 2300 kilometers and there are more than 2900 individual coral reefs. It covers approximately 133,000 square miles. The Great Barrier Reef is the one and only structure that has been made by the living organisms and that can be seen far away from the outer space. The millions of tiny organisms known as the coral polyps have built this structure which supports a huge aquatic life system and has been recognized as one of the World Heritage Site in 1981. It was labeled as one of the seven natural wonders of the world by CNN. The Great Barrier Reef is the State Icon of Queensland as stated by the Queensland National Trust.

The Great Barrier Reef ecosystem is facing a complete collapse from global warming and climate change. This man-made disaster is increasing temperatures and changing the chemistry of the ocean which leads to coral bleaching and creates a perfect environment for the crown-of-thorns starfish. The predatory starfish moves in and often devastate a weekend coral system. The coral cover of the reef has lost more than half of all organism since 1985 as shown in the reports published by Proceedings of the National Academy of Sciences in 2012. The area is protected from any kind of human activities like fishing and also the tourism is limited so that the natural structure does not get exploited.

The Great Barrier Reef is sacred for the people who dwell in the Torres Strait Islands and for the Aboriginal Australians.
 It is a world famous tourist spot that generates economic activities for the many small businesses and generates millions in tourism.

Ecology of the Great Barrier Reef

The Great Barrier Reef is the home to many endangered and vulnerable species which are even endemic to this coral Reef system. The Great Barrier Reef is home to the humpback whale, dwarf minke whale and the Indo-Pacific humpback dolphin and many such other tiny species of porpoises, dolphins, and whales. The reef system supports a large population of dugongs. Other than these there are several species of snapper, eighty-four species of spawns, red-throat emperor, coral trout, red bass, clownfish and forty-nine species of the mass spawn. In the northern and the southern sections, up to 50 meters in the warm waters of the reef systems lives over seventeen species of sea snakes.

The species of sea turtles like the hawksbill turtle, leatherback sea turtle, Olive Ridley, flatback turtle, green sea turtle and loggerhead sea turtle come to the reef systems for breeding. The green sea turtles are divided genetically between the northern and the southern part of the reefs. There are fifteen species of seagrass grows in the seabed of the ocean like Halodule and Halophila that provides fish habitats and also attracts turtles and dugongs. The coast near the reef is home to many saltwater crocodiles which live in the salt marshes and the mangroves and also to a large species of skates, sharks, stingray, and chimera live on the reef system. Over 5000 species of mollusk have been found on the reefs which include cone snails, giant clam, and various nudibranchs. Nine species of sea horses, seven species of frogs and over 50 species of pipefishes has been found in the Great Barriers. More than 215 species of birds migrate to the reefs each year and add to the diversity of the region.

Threats to the Great Barrier Reef

Ocean warming and elevated temperatures have resulted in coral bleaching which has become an annual occurrence now. They are becoming susceptible to diseases that result in ecological effects for the communities in the coral reefs. The declining water quality and pollution in the water as also contributed largely to the death of many species of organism. The loss of coastal wetland has also snatched away many habitats of the organisms.

The Kelp Ecosystem and its 

The under ocean ecosystems that have a high density of kelp are known as the kelp forests. This ecosystem in one of the most dynamic and productive ecosystems on earth, there are other kelp ecosystems with areas that are comparatively smaller than the kelp forest that are known as kelp beds.

The Architecture of the Ecosystem

The physical structure of the kelp influences the species that are associated and it defines the structure of the community. The architecture of the kelp ecosystem is based on this physical structure. The structure of kelp forest ecosystems is divided into three guilds and among that two guilds are occupied by algae.
  • Canopy: floating canopies and large species constitute this guild of the kelps which extends up to the surface of the ocean like Alaria and Macrocystis 
  • Stipitate: these generally grow in the dense, aggregated areas and extend up to a few meters above the sea bed. 
  • The kelps that are near the sea floor or along it are called Prostrate like the Laminaria. 
Other algal species like the articulated functional corallines, filamentous algae, and the foliose functional groups assemble the benthic group that lies along the bottom of the ocean and it also consists of the sessile organisms.

The coralline algae extensively and directly cover the geologic substrate which is known as the Encrusting.

The prostate and stipitate kelps are called the understory canopy like the Macrocystis canopy. Within the forest, the kelp species co-exist. The understory species like the Pterygophora and Eiseniafloats a few meters above the seabed. The assemblage of the foliose red algae which is the benthic layer lies below this level. The canopy assembles over these two layers. They form a microenvironment system which is similar to the terrestrial ecosystem that blocks the sunlight partially and makes the middle part shady and the sea floor gets darkened. Many organisms survive on different guilds and they live in different guilds because each guild has a different kind of habitats for different species. And the existences of these organisms in the different guilds also depend on the kelp morphologies. For example, the skeleton shrimp which like Caprella California, the nudibranch Melibe leoninalie closely to the surface in the Macrocystis pyrifera forest of California. Within the stipitate understory other fishes, rockfish Sebastes spp., Brachyistius frenatus which is the kelp perch were found. The kelp holdfast constitutes the brittle stars, Tegula spp. that is the turban snails. Under prostrate level lives the Sea urchins, abalone, and other herbivores. Among these assemblages live the sea stars, fishes, and other hydroids. In the encrusting coralline regions reside various echinoderms, gastropods, and other solitary corals. And the animals like the marine mammals and pelagic fishes which feed on the organisms that reside on these guilds, come and interact near the edges.

Trophic Level of the Kelp Ecosystem

The primary producers’ growth is driven by the abiotic conditions like the available amount of nutrients and sunlight. They transfer energy to higher trophic levels where the consumers dwell. The upwelling oceanographic zones provide more amount of nutrition to the organisms and thus the occurrence of the kelp is correlated in such a way. The herbivores are thus supported by these kelps and the consumers at the higher levels feed on such herbivores for survival. In contrast, the predators control the population of the lower species or their biomass by consuming them, in the top-down processes. The resources that are the key sources of survival for the lower level organisms are non-limiting and thus they flourish. The population of the herbivorous sea urchins are controlled by the sea otters that prey on them in the Alaskan Kelp forests. The population of the sea urchins grows at a faster rate when the sea otters are exploited by any human or other kinds of interference. The sea urchins get out of the predatory control completely. Now the herbivore pressure increases rapidly on the local stands of kelp. So to maintain a balance in the food webs is the most important feature of the kelp ecology.

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