The one common characteristic that the tropics have in common is that the temperature is warm. The daily temperature usually changes more than the temperature average of the year. This is because the sun falls more directly on the topics than on other regions. However, depending on the region there will be changes in rainfall. Rainforest receives more rain than tropical savannas (more than 200 cm a year). Because of this savannas are more suitable to fires in the dry season. Some plants have adapted to be able to survive these fires, and often have visible scarring from fires. The animals have also adapted to the dry conditions. Because droughts are localized the animals migrate around the savanna. The soils are often acidic and are poor in nutrients. The soils are sandy and coarse textured. In addition, some savanna may become waterlogged during the year so the plants have to be adapted. For this reason, there is less plant diversity in savannas.
Rainforests, on the other hand, have to deal with excess moisture. Moisture can cause fungus and molds to grow. Some plants have developed drip tips because of this. Drip tips are sharp points on the end of a leaf that let water drip off the leaf. Leaves are concavely shaped so that water will run off of them. Leafs also have smooth edges rather than teeth to prevent water build up. Water build up would cause fungi and molds to grow on the leaf which would block sunlight and decompose the leaf. The soil is often moist and clay-like. Many monkeys are well adapted to live in the rainforest. They rely on the fruit which is in constant supply. In addition, new world monkeys have developed tails so they can easily navigate the tall canopy. Other animals have adapted to the heat by becoming nocturnal. Bats are an excellent example of this adaptation.
Like the savanna and the rainforest, coral reef requires fairly specific environmental factors in order to exist. The temperature is usually between 21-29 degrees Celsius. The reason this range is idea is that coral is actual a mutualistic relationship with algae called zooxanthellae. If the temperature increases too much then the zooxanthellae starts to produce toxic compounds to the coral and so the coral has to kick it out. Nutrient levels must be low because otherwise, microalgae will out-compete the corals. This is why the coral must be in a relationship with zooxanthellae because it lives in nutrient-poor water. In order for the zooxanthellae to undergo photosynthesis, the water must have a high light availability. Plating coral has evolved its shape so that it can absorb more light because it has a large surface area. In addition, the water cannot be too acidic or the rate of decalcification will be too great for the coral to form. The coral reefs provided great nursing habitat for dolphins, and whales raising their young. However, they do not have much food. Therefore these animals have adapted to use the reef as nursery habitat but migrate north to waters with more food. Because coral reefs have nooks many animals, particularly fish have adapted to live in these. They have flat bodies that are highly maneuverable.
The following was my environmental studies senior thesis.
Storm water runoff from agricultural areas carries excess nutrients with it, which leads to dead zones in nearby lakes. Lake Champlain is the sixth largest lake in the United States, and is facing issues related to excess nutrients from farms. Research related to farms has focused on runoff related to manure spread on fields. One area not previously addressed is manure management on farms. There are two main types of manure pit styles on dairy farms; enclosed and, unenclosed. Three farms of each of these types were analyzed for nutrient runoff during storm events. Four key factors linked to nutrient runoff were analyzed through field sampling; phosphorus, dissolved oxygen, nitrate, and ammonium. The study took place in the Lamoille River Watershed in Vermont which feeds into Lake Champlain. Baseline data was collected before storms and samples were also collected after storms. The goal of this study was to identify a manure pit management style that minimizes nutrient runoff. While the data indicated that a manure pit that lacked a confining wall impacted phosphorus, ammonium, and nitrate, there was no significant impact on dissolved oxygen from such pits. However, manure pits had relativity low impact on the streams overall; other more important factors may be soil erosion, manure spreading, and septic tanks.
Bats have the largest number of species of any group of mammals, as many as 1,200 species. All of these bats are found in the order Chiroptera. Chiroptera contains the two suborders Megachiroptera and Microchiroptera. Megachiroptera contains the Old World fruit-eating bats which Microchiroptera contains the so-called echolocating bats. Recently researcher discovered the Old World fruit-eating bats actually use a very basic method of echolocating themselves, they use sonar clicks from their wings to help them navigate at night. The echolocating bats are found on every continent except Antartica. Megachiroptera and Microchiroptera differ from each other by their soft tissue structures. Member of Microchiroptera have a tragus, which is basically a fold of the inner ear. They also have an internal complex echolocation system. BEcause the difference between the two suborders is found in soft tissue organs the natural history of these differences is unknown because soft tissue doesn’t leave a fossil record. Megachiroptera only contains the family Pteropodidae. Microchiroptera contains 7 subfamilies; Emballonuroidea, Rhinopomatoidea, Rhinopomatidae, Rhinolophoidea, Vespertilionoidea, Molossoidea, Nataloidea, and Noctilionoidea. These are further broken down into at least 17 families. I am going to go over one family from each subfamily.
An endemic organism is one that is found only within a certain region. There is a rush that goes along with seeing a species that can be found nowhere else. Georgia is actually home to a handful of endemic species, most of which are aquatic. The Altamaha Spinymussel (Elliptio spinosa) is a freshwater mussel only found in 3 river systems in Georgia. Freshwater mussels are actually the most imperiled group of organisms in North America. There are a large number of reasons why this could be but one thing is for sure, mussels are dying in large numbers. To give you an idea of how rare some species can be, when I worked in a mussel lab we would actually pit tag some species so that we would be able to find them later. In the time span of less than a year, our most productive mussel bed had completely died. For the Altamaha spinymuseel, it is estimated that populations have declined 50-70 percent and it only occurred in 7 sites out of 120 sites that were sampled after 2000. Few juveniles or small individuals were found in these surveys. It used to be found in the Ohoopee River system and Oconee River in addition to the Altamaha River system. In the Ohoopee and Oconee, the mussel is thought to be extirpated or populations are so small it is undetectable. All freshwater mussels, expect the Salamander mussel (Simpsonaias ambigua), have a stage in their life-cycle in which they are fish parasites. The glochidia, or baby mussels, attach to fish gills and develop there until they become juveniles. This is how they expand their range.
The Etowah darter (Etheostoma etowahae) is another species that is only found in the Peachtree state. It is a small fish that is about 2 inches long. The fish occurs a less than 10 locations in the Etowah River system. They prefer swift riffle habitats that have either cobble or gravel. There is likely less than 10,000 adults and at sites sampled the darter represents only a small part of the community. Because of this and the expansion of metro Atlanta into its habitat, the species is protected as an endangered species both federally and at the state level. They look very similar to the closely related greenbreast darter (Etheostomajordani) and lipstick darter (Etheostoma chuckwachatte). Some scientists say that the Etowah darter and greenbreast darter differ by the red markings the Etowah darter has on its sides. This difference between species has been recently challenged with some saying you can’t tell the species apart without genetic testing. The Etowah darter does not co-occur with the lipstick darter so range maps can be used to determine which species you are looking at.
The United States has the most turtle species out of any country in the world (51 species). Common snapping turtles (Chelydra serpentina)are one of the most easily identified of these 51 species. In 5th grade, our class pet was even a snapping turtle baby that someone had found in a parking lot. They have a wide range of areas that they live in North America; basically all of the U.S. minus the west coast and Texas. Sadly there is also a wide range of misconceptions to go along with their wide geographic range. The biggest misconception is that they are aggressive and should be killed if seen. Others have negative views of the turtles because they kill game fish, which is true but have a minimal impact on populations. Generally, they are only aggressive on land as it is hard for them to walk on land. They tend to only be found on land during the breeding season when females go in search of sandy patches in which to lay their eggs. These sandy patches are often found along roads. If you see a snapping turtle in the road if you decided to move you should know they have a long reach with their neck and their claws are also very sharp. Typically I just stand in the road with the turtle until it safety crosses. If the turtle is a baby you can carefully pick it up and place it near a waterbody where it can hide from predators.
In the cell cycle, cell division functions in reproduction, growth, and repair. The two forms of cell division are mitosis and meiosis. Mitosis requires the distribution of identical DNA to two daughter cells. Meiosis yields four nonidentical daughter cells, each with half the chromosomes of the parent. The purpose of meiosis is to produce cells for reproduction, and as you want the offspring to have the same number of chromosomes as the parents’ sex cells need to have half the number of chromosomes as the parents. A cell duplicates its DNA, moves the two copies to opposite ends of the cell, and then divides into two cells. This genetic information that makes up the cell’s genetic information is called its genome.
The genome is made up chromosomes. Every eukaryotic species has a characteristic number of chromosomes (packaged DNA) in each cell nucleus. Eukaryotic chromosomes are made of chromatin which is a complex of DNA and protein. When a cell is not dividing chromosomes are chromatin fiber in the nucleus. Each duplicated chromosome consists of two sister chromatids, which appear when cell divisions are about to take place. The chromatids are attached at what is called the centromere. After the chromatids divide mitosis is followed by division of the cytoplasm or cytokinesis.
R-selected and K-selected species are terms that biologists use to describe animals’ reproductive strategies. Either an animal produces a large number of offspring, and it is a numbers game for those offspring, or the animals have few offspring and invest a significant amount of time in those offspring. R-selected species are those that favor a large number of offspring. R-selected species include insects, amphibians, many fish, and reptiles. They tend to be smaller organisms, so the energy used to make each individual is low, and they live in unstable environments. They also have shorter lifespans and reach sexual maturity quickly. They have a type III survivorship pattern which means that earlier in life, more organisms will die than later on in their life. In these species, the number of offspring is crucial because it directly impacts the population size. Continue reading →
The following post is a reflection on a field trip I took to Belize as part of my tropical ecological class.
In the marine environments, there were three main ecosystems that we explored; seagrass and sand flats, coral reefs, and mangrove forests. Of all of these, the coral reefs had the highest species richness due to their high primary productivity. This is due to the dual nature of coral, that of a producer and a predator. Coral itself is a tiny animal that hunts plankton with tiny barbs. Most coral tissue also contains an algae called zooxanthellae which provides energy to the coral via photosynthesis. This creates available energy for others, like parrotfish that eat corals. It also allows the coral to create a structurally complex area. The mangroves have the next highest level of primary production and are almost as structurally complex as the coral reefs. On the other hand, the sandy and grassy flats have little structure to them. When snorkeling there very few species besides 3 species of ray were seen.
An understanding of physical properties of soil leads to an understanding of how other processes may take place. The majority of these properties also change very slowly, therefore, a small difference can mean a lot. Soil texture is determined based on the proportions of the soil that contains sand, silt, and clay. This effects specific surface area, water relations, tillage, erosion, agrichemicals relations, and environmental considerations related to soil. In particular specific surface area plays a key role in determining the interface or contact zone between particles and their surrounding environments. Organic content is important for soil fertility, water absorption, and nutrients for the soil. Water content is important as plants need water to grow, and it is also needed to help replace water in the water table. Color helps to determine what the specific context of the soil may be. For example, a reddish soil indicates exposure to oxygen and possibly iron. Lastly, pH affects the surrounding environment of the soil, and its ability to hold minerals such as calcium.
There are basically three schools of thought when it comes to classifying soils; engineering, soil science, and OSHA. I am going to go into the most detail with the soil science approach because it is what I am most familiar with. Unified Soil Classification System (USCS) is the most common engineering classification system used in North America. It breaks soils down into three groups; coarse-grained soils, fine-grained soils, and high organic soils. Coarse-grained soils are sand and gravels, while fine-grained soils are things like clay and silt. High organic soils are peat soils, which I discussed in my wetlands overview post. These three groups are then further broken down. The coarse-grained soil classification is broken down into sand and gravel based on the particle size. Typically this is done using a stack of sieves that sort soil by particle size. The top sieve has the largest mesh, and progressively the mesh gets smaller and smaller. The stack can be shaken by hand or placed in a shaker.
Recently I had the joy of going birding with a local group in a small park in Brookhaven, Georgia. We saw over 33 species.
I was surprised that members of the group were excited to see double-crested cormorant (Phalacrocorax auritus). There is a common misconception about them that I have heard mostly due to the increase in their population, particularly on Lake Champlain in Vermont, where I grew up. When DDT was banned in 1972, it opened the door for the cormorant population to expand and it did. On Lake Champlain, the populations went from one breeding pair in 1981 to over 4,500 breeding pairs. Cormorants are piscivorous, meaning that they consume fish. Their population growth raised concerns with fisherman, one of which who told me that cormorants are an invasive species. To further this belief, the state of Vermont in 1999 began to oil the eggs of the birds. This prevents gas exchange and kills the birds in the eggs. The birds prefer to eat fish that are between 3 to 6 inches. On Lake Champlain, it has been shown that most of their diet is yellow perch (Perca flavescens) and alewives (Alosa pseudoharengus). Rarely are trout and salmon found in their stomachs, except when the fish are released annually into the lake from fish stocking facilities.
We also saw 17 tufted titmouse (Baeolophus bicolor), which I learned to identify by their classic peter-peter-peter call. They are year-round residents of this area and in most of the Eastern United States. They often flock with chickadees, nuthatches, and woodpeckers. Flocking means that predators are less likely to capture one as more birds are on the lookout for them. Food gathering efficiency is also increased by flocking behavior. In addition, there is reduced inter-species aggression which reduces competition. If you would like to attract tufted titmouse to your property they visit bird feeders and also benefit from nesting boxes. It is important to place a guard around nesting boxes to protect from predators and to place the boxes up well before breeding season.