"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:
A: Cumulative recorder
Explanation:
B. F. Skinner was a psychologist, author, behaviorist and inventor of Operant conditioning chamber and Cumulative recorder. The purpose of cumulative recorder was to study the rate of operant conditioning. It is a process in which behavior of an organism is modified or an organism is conditioned to perform a specific behavior through giving punishment or reward.
For example: We teach a kid that he should not touch a hot stove because it will burn his hands, or we give him a box of candies to perform a specific task or behave in a certain way. Skinner used Cumulative recorder to find the effect of certain factors on behavior or response of an organism For example: the rate at which lever was pressed by a monkey to get bananas etc.
Hope it helps!
Gametes are the cells in human body used for reproduction, such as sperms or eggs, and somatic cells are the other body cells, such as muscle cells, skin cells and all other.
First, they have different number of chromosomes. Gametes have only one set of chromosomes, while somatic cells have a complete 2 set of chromosomes. This is because fertilization requires 2 gametes joining together and this will help maintain the correct amount of chromosomes at last.
Second difference between them is that gametes are products of meiosis, while somatic cells are products from mitosis. Both are types of cell divisions but meiosis produces 4 genetically different cells while mitosis produces 2 genetically indentical daughter cells.
Answer:
The parent's genotypes are:
Ddpp - tall, white parent
ddPp - dwarf, purple parent.
Explanation:
This question involves two different genes coding for height and flower color in pea plants. The alleles for tallness (D) and purple color (P) are dominant over the alleles for dwarfness (d) and white color (p) respectively.
According to this question, a tall plant with white flowers is crossed with a dwarf plant with purple flowers to produce the following proportion of offsprings: 1/4 tall purple, 1/4 tall white, 1/4 dwarf purple, and 1/4 dwarf white.
Since some of the offsprings contain recessive alleles for both or either genes, the dominant traits of the parent is controlled by an heterozygous genotype. This means that the tall plant with white flowers has a genotype: Ddpp while the dwarf plant with purple flowers has the genotype: ddPp. In a cross between Ddpp × ddPp, 1/4 of each combination of alleles is produced in the offsprings (see punnet square in the attachment).
Answer:
Mammals
Birds
Explanation:
The Organs which perform same function and looks but they are different in their structure from each other are called as analogous organs.
Organs are the structures that made up of two or more tissues organized to carry out a particular function.
An organ or bone that appears in different animals with same function is called homologous structure.
Homologous organs have similar origin n basic structure but perform different functions in different organisms. Analogous organs are different in basic structure but perform same functions.
Different animals have bones that appear very similar in form or function and seem to be related.
Examples
The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale are homologous structures. They are different and have a different purpose, but they are similar sharing common traits.
The forelimbs of all mammals have the same basic bone structure.The structures are similar because they evolved to do the same job. For example, the wings of bats and birds.
