The rods are photoreceptor cells that respond to the longest wavelengths of light, ranging from approximately 500-700 nm. Rods are responsible for vision at low light levels (scotopic vision).
The cones, on the otehr hand are the other <span>photoreceptors in the human retina that </span>are active at higher light levels (photopic vision).
An ecologist studying plants in the desert performed the following experiment. She staked out two identical plots, which included a few sagebrush plants and numerous small, annual wildflowers. She found the same five wildflower species in roughly equal numbers on both plots. She then enclosed one of the plots with a fence to keep out kangaroo rats, the most common grain-eaters of the area. After two years, to her surprise, four of the wildflower species were no longer present in the fenced plot, but one species had increased dramatically. The control plot had not changed. Using the principles of ecology, propose a hypothesis to explain her results.
Explanation:
- This example highlights the impact of plant predation on species selection. In the fenced off plot animal predation is not a factor on plant selection.
- In this case plants will compete for resources only with each other and in this case one plant had a selective advantage over the other 3 species of plants. In the plot exposed to animal predation the ratio of the four species is equal.
- This is likely do to an increased preference of animals for the plant species that dominates in the fenced off plot and/or anti-animal predation tactics by the other three species.
a.Hypothesis: kangaroo rats are keystone species
-Reintroduce kangaroo rats (and the other locally extinct species)
-Should observe equilibrium re-established
b.Hypothesis: kangaroo rats exert top-down control on community
-Reintroduce kangaroo rats (and other locally extinct species)
-Increase kangaroo rat population in other plot
-Decrease (but don't eliminate) kangaroo rat population in other plot
c.Hypothesis: Locally extinct species inferiorly competed with the extant species of plant
-Remove surviving species from other plot (and remove kangaroo rat population)
When the heated part of the mantle rises through the cooler part , this is an example of Convection.
One characteristic of life is that living things have different levels of organization
-They have both molecular and cellular organization
- They must have the ability to organize simple substances into complex ones.
- They organize cells at several types of levels, namely:
(a) Tissue- a group of cells that perform a common function
(b) Organ - A group of tissues that perform a common function.
(c) Organ system- a group of organs that perform a common function.
(d) Organism- any complete living thing.
