Josyvan , 7/9/2007
Question: How scientists study Evolution?
Evolution of Air-Breathing OrganismsBoth the lung structure of air-breathing organisms and the swim bladders of most modern fishes evolved from paired air sacs of primitive bony fishes. In theJosyvan , 7/9/2007
Question: How scientists study Evolution?
Fruit Fly Laying EggThe small vinegar flies of the family Drosophilidae, commonly called fruit flies, have been exceptionally useful in scientific research. Their short reproductive cycle (aJosyvan , 7/9/2007
Question: How scientists study Evolution?
DNA MoleculeA DNA molecule consists of a ladder, formed of sugars and phosphates, and four nucleotide bases: adenine (A), thymine (T), cytosine (C), and guanine (G). The genetic code isJosyvan , 7/9/2007
Question: How scientists study Evolution?
Analogous and Homologous StructuresStructures that are similar due to evolutionary origin, such as the forearm bones of humans, birds, porpoises, and elephants, are called homologous.Josyvan , 7/9/2007
Question: How scientists study Evolution?
OstrichesThe distribution of the world’s flightless birds, called ratites, is indicative of the shifting of continents in the Earth’s distant past. Ratites evolved on a landmassJosyvan , 7/9/2007
Question: How scientists study Evolution?
Midge Fly Caught in AmberPaleontologists can learn about prehistoric life by studying the remains of ancient insects, such as this midge fly, trapped in tree resin when they were alive. TheJosyvan , 7/9/2007
Question: How scientists study Evolution?
Species do not change overnight, or even in the course of one lifetime. Rather, evolutionary change usually occurs in tiny, almost imperceptible increments over the course of thousands ofJosyvan , 7/9/2007
Question: How Scientists clone cells?
Scientists initially made cloned cells in the laboratory by letting a single cell divide into a population of genetically identical cells. In this process scientists put the original cell in aJosyvan , 7/9/2007
Question: How Bacteria Function
Bacterial cells often can survive by exchanging DNA with other organisms and acquiring new capacities, such as resistance to an antibiotic intended to kill them. The simplest method of DNAJosyvan , 7/9/2007
Question: How Bacteria Function
In response to limited nutrients or other harsh conditions, many bacteria survive by forming spores that resist the environmental stress. Spores preserve the bacterial DNA and remain alive butJosyvan , 7/9/2007
Question: How Bacteria Function
The simplest sort of bacterial reproduction is by binary fission (splitting in two). The bacterial cell first grows to about twice its initial size. Toward the end of that growth, the cellJosyvan , 7/9/2007
Question: How Bacteria Function
Bacteria reproduce very rapidly. Replication in some kinds of bacteria takes only about 15 minutes under optimal conditions. One bacterial cell can become two in 15 minutes, four in 30 minutes,Josyvan , 7/9/2007
Question: How Bacteria Function
All organisms have some capacity to adapt to environmental stress, but the extent of this adaptive capacity varies widely. Heat, cold, high pressure, and acid or alkaline conditions can allJosyvan , 7/9/2007
Question: How Bacteria Function
The metabolic activities that enable the cell to function occur in two ways: anabolism and catabolism. Simply put, anabolism is the manufacture of complex molecules from simple ones, andJosyvan , 7/9/2007
Question: How Bacteria Function
Bacterial cells, like all cells, require nutrients to carry out their work. These nutrients must be water soluble to enter through pores in the cell wall and pass through the cell membrane into