In some large groups of plants, including dandelions, oaks, and willows, the biological species concept is complicated because the process of allows gene flow to occur between good that can be easily distinguished based on appearance.

A) hybridization; morphospecies
B) hybridization; ecological species
C) allopatric speciation; ring species
D) polyploidy; evolutionary species
E) polyploidy; ring species

A) hybridization; morphospecies

Explanation:

The biological species concept is the concept which can define a species as an individual of a large population which can interbreed and produce an offspring in a population. The concept was given by Ernst Mayr.

Morphospecies refers to the species which can be characterised by the differences in their morphological features like in the Oak, willows and the dandelions.

The biological species concept is not valid or complicated in the case of the morphospecies like in the Oak, willows and the dandelions as the individuals of these three population can exchange their genes through the process of hybridization.

Thus, Option-A is the correct answer.

silty loam

hope this

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!