Biosphere

Today we covered the transport of sugars in phloem and watched some more of a movie about plants. First the phloem. At the beginning of the sugar transport sucrose flows through symplasts of the producer cells untils it reaches the phloem. Once the sugar reaches the phloem it is actively contransported with H+. This creates a water potential gradient. The sieve tubes that have the sucrose flowing into them have a low water potential and so they absorb water until they have a high water potential. The other end of the sieve tube pushes water out and creates a lower water potential. The combination of the differing water potentials and pressure build up at the source end of the sieve tube push the water and sugars to the other end of the phloem. The receiving end or “sink” then absorbs the sugars and sends the water to the xylem.
During the video we learned about some pretty weird plants and their relationships with their pollenators. Two in particular stood out above the rest. First, one of the orchids produced a scent that smelled like rotting flesh. This attacted flies and when they crawled down to where the plant smelled like flesh, they were trapped. Eventually they were set free, but a lot of the flies died during the two day waiting period. The second interesting thing we saw in the video was the ant-aphid relationship. Apparently ants really like the liquid that aphids produce so they protect the aphids and harvest some of the liquid for the queen. Overall the video taught us that there are many ways for plants to spread their pollen and that there are all sorts of go-betweens that they can use.

We did a lab, and that’s it. 

Today we took a quiz, and then took notes. In the notes we covered transpiration and stomates function and regulation. Plants should be in a hypotonic environment so that the water can move into the low potential roots, from the high potential soil. The roots have a system to intake water by first pumping the minerals in, to create the gradient to bring the water in. The cell wall is hypertonic therefore allowing the water in, to pump to and through the membranes, following the apoplastic route most commonly. (Found on page 755) The endodermis is lined with the Casparian Strip, which is a “wall” that the water hits that forces the water to go though the ell membrane and into the symplast to be filtered and forced into the xylem vessels, gaining control over the process. A symbiotic relationship occurs between fungi and plants in some cases. This is to create more surface area for the absoption of water and minerals for plants, and gives the fungi a “home” and minerals through the connection. It also increases the volume of soil, and the transport. The fibers of the fungi that receive this water are called mycorrhiza. Transpiration is the movement of water in the plant, which incurs a pull from the leaves and a slight push from the roots. The pull involves adhesion and cohesion with hydrogen bonding. The water potential is high in the roots and low in the leaves, forcing the water up with the water potential. Next is the stomata. They help to regulate the balance between the amount of water and the amount of CO2 in photosynthesis. The opening is regulated by microfibril mechanisms of guard cells, which is in the cell walls of those cells. When the cells are elongated, the stomata is open, and when they shorten the stomata closes to prevent water loss. The actual process of opening and closing is regulated by potassium, proton pumps uptake potassium elongating the guard cells, opening the stomata. The process of osmosis makes water leave and the cells become flaccid. This process can be cued by many things, such as light, which triggers the uptake of potassium. It can also start from the loss of CO2, when photosynthesis has already depleted it, or with the circadian rhythm which is a 24 clock cycle. This video is great for stomata information. -alex kulish )[kml_flashembed movie="http://www.youtube.com/v/cFX4JrsPaUs" width="425" height="350" wmode="transparent" /]

Today we learned the basics of transportation in plants.  Many materials are transported for the plant to be fully functional.  Items such as water and minerals are transported from the roots to the shoot system through the xylem.  A process known as transpiration pulls the materials using negative pressure, evaporation, adhesion, and cohesion.  Food, primarily sugars, are transported from the leaves and the stem to the roots via the phloem.  A concept known as bulk flow describes how the calvin cycle in leaves loads sucrose into the phloem sieve tubes and pushes the materials down using positive pressure.  Gases are also transported in and out of the plant through gas exchanges, like photosynthesis and respiration.

Transportation occurs at different scales.  Cellular transport utilizes active transport and the proton pump.  Short-distance (cell-to-cell) transport takes placee in one of three ways.  In the symplastic route, materials are transported through plasmodesmatas, or junctions which connect cytosol of neighboring cells.  This route is efficient, however, the plant has no control over transportation.  In the apoplastic route, materials only travel through connected cell walls without ever entering crossing the cell membrane.  This is the fastest route for transportation.  The transmembrane route is the pathway by which materials repeatedly cross the plasma membranes.  This is the slowest route for transportation, but the plant is given a great deal of contol. 

Finally, long-distance transport utilizes the xylem and phloem and external forces such as transpiration.

All in all, transportation proves to be extremely important in keeping the plant healthy and alive.

-Allison Knott

Today in class we watched an informational/humorous slide on the affects of love. The slide went over basic concepts of how species are attracted to one another (such as, masculinity and appearance). We also worked on our pasta labs today. We were required to organize many different types of pasta into a geneology tree. This allowed the students to get very creative and use their knowledge of evoluntionary theory. After starting the pasta lab and viewing the love slideshow, we all watched an interesting and extremely gross video on slug mating. We were able to see how diverse sexual reproduction truly is and how many elements are involved. Below is a copy of the slug mating video.

[kml_flashembed movie="http://youtube.com/v/vtgPAQTJLQs" width="425" height="350" wmode="transparent" /]

-Austin Black

Today we shared our different examples of pasta family trees. No two were the same. They were organized by everything from shape to environmental factors (thank you Zach and Austin). After this we reviewed for our test on Thursday. We discussed the heterozygous advantage in greater detail. Sickle cell anemia demonstrates this. The gene for sickle cell anemia also provides resistance to malaria. This resistance also applies to people who are heterozygous for it. As sickle cell anemia is a recessive disease, people who are heterozygous have a better chance of survival because they are not as susceptible to the effects of the sickling as people who have the full blown disease.

There are several definitions for species. One of the most popular is the biological species concept. It was defined by Ernst Mayr. This concept states that a new species is formed when a population can interbreed and reproduce viable, fertile offspring with only members of that population.
The diversity and taxonomy of species can be classified using a tree. The different species are the smallest units at the ends of the branches. The species are the basic unit for organizing and categorizing living things, and the smallest unit by which diversity is measured.
According to the biological species concept, new species are created when biological barriers that keep members from producing viable offspring appear. Pre-zygotic barriers are obstacles that keep sperm and egg from meeting.They include ecological isolation and temporal isolation. Ecological isolation occurs when two species live in the same area but in different habitats. An example would be the terrestrial and water garter snakes. Temporal isolation happens when species breed at different points in time. For instance, the eastern and western spotted skunk. The eastern spotted skunk mates in late winter and the western spotted skunk mates in the late summer.

In class, we organized different kinds of pasta to represent different species of a single “food kingdom”. The activity allowed us to understand the concept of hierarchical classification. A major objective of systematics is to group species into broader taxonomic categories. Biology’s taxonomic scheme formalizes our tendency to group related objects.

Beyond the grouping of species within genera, taxonomy extends to progressively broader categories of classifcation. For instance, related genera are placed in the same family, families are placed into orders, orders into classes, classes into phyla, phyla into kingdoms, and kingdoms into domains. In our case, we grouped all of the pasta samples into the domain eukarya, kingdom plantae, so on and so forth.

The following picture is of a phylogenetic tree which reflect the hierarchical classification of taxonomic groups nested within more inclusive groups.

Today we discussed different evolutionary trends. First we went over analogous traits, which are basically similar structures between two species that are not closely related, and this is often attributed to convergent evolution. This is seen between such animals such as birds and bats, which can both fly, but they are not closely related. We then went over parallel evolution which is when animals adapt to fill similar niches and therefore develop similar adaptations without being closely related. Mimicry is when convergent evolution is based on similar appearance (often for protection purposes). Finally, coevolution is when species evolve along with one another for survival. This is seen in predator-prey relationships, parasite-host relationships, and flower-pollinator relationships.

    On the 30^th we studied the bottle neck effect and the effect it has on animal populations. The bottle neck effect is the process by which a population’s gene pool looses allele diversity as a result of some sort of disaster.  As a result, the surviving members of said population will have a narrowed gene pool allowing for less variation. The bottle neck effect has all but extinct species such as the cheetah, survivors of no less than two bottle neck effects. Because the bottle neck effect causes a loss specific allele from the gene pool of a species the remaining animals will have a hard time adapting, and thus surviving.

    We also studied gene flow. Due to migration, two distinct populations of a species may assimilate into one. To begin with, the populations may have been quite distinct from one another but over time, assuming migration is taking place between the two populations, the two gene pools will merge together and become indistinguishable. This process is called gene flow. Humanity has seen these effects; an individual can travel half way around the world in a matter of hours, as can their genes. Some postulate that, many years down the road, all of the human populations around the world will synergize into one.