"In the early days of germ theory, contagious diseases
were thought to be caused by fungi or bacteria. In the 1890's, Dmitri
Ivanovski filtered extracts from diseased tobacco plants and discovered
that the disease could be transmitted to new plants through the
filtrate. He concluded that the disease was caused by particles smaller
than bacteria; the tobacco mosaic virus", is partially correct. Dmitri
Ivanovski discovered that filtered extracts from diseased tobacco plants
could be transmitted to new plants through the filtrate. However, it
was Dutch microbiologist Martinus Beijerinck who, while replicating
Ivanovsky's experiments, proved that the filtrate contained a new
infectious agent. Beijerinck named this agent a virus.
Answer:
1.Temperature
2.Moisture
3. PH: acidic or basic concentration
Explanation:
Different microorganism grow at different temperature. For example, many human-disease-causing microbes have an optimum temperature of 37C, and most of the bacteria do not grow at temperature higher than 45C. This means that any temperature lower than 45C will favor the growth of certain bacteria while higher temperature may cause death or reduction in the population of most. Hence, the effect of temperature on these organisms.
Water is required to dissolve the cell substances in microorganism just like higher animals. while some can survive under an extremely dry condition, most can't and this could result in death or reduction in population.
PH, a measure of the hydrogen concentration in a solution for most microorganism is between 6-8, too much of acid or base could disrupt the activities of these organisms and a maintained range ensure an optimal survival.
Answer:
In general, negative selection eliminates from the population very harmful changes to proteins that kill or stop reproduction. ... The authors also found a correlation between genes predicted to be under negative selection and genes implicated in certain hereditary diseases
Explanation:
Answer:
Two adaptations of Darwin's Finches that helped them to survive are:
- Behavioral adaptations to use tools for foraging.
Explanation:
There are fourteen species of Darwin's finches that originated from a single species of ground dwelling seed eating finch.
These Finches occupied different niche in the Galapagos island and were widely studied by Darwin.
These finches are one of the best Examples of Adaptive radiation.
Studies state that during severe drought in Galapagos island most vegetation dried out and a few softer seeds were left.
These few seeds were quickly fed upon by the birds and only dry , hard seeds were left.
Only birds who had large and hard beaks could feed on these hard dry seeds.
To Ensure survival the Finches developed adaptations which resulted in hard and large beaks so that they can feed on those dried hard seed.
Some groups started feeding on insects and got their beaks adapted to capture and kill insects.
Second line of adaptation included changes in behaviour and cognitive intelligence where birds started using tools for foraging.
Answer:
They are thick, strong and made up of thousands of tubulin which are spiral in shape.
Explanation:
In eukaryotic cells, they have microtubules which are fibres serving as tracks for cell to cell transport and regulate the shape of a cell.
Microtubules are different from other cytoskeletal filaments because they possesses a cylindrical shape with the tube having a larger diameter of 20-25 nm as compared to microfilament that have a diameter of 3-6 nm.
Microtubules are made of subunits of proteins called tubulin named alpha and beta that is not present in other cytoskeletal filaments.
