Evolution
The history and science of origin and evolution comprise two events, the beginning of life and expansion of life. Our earth originated about 4.5 billion years ago. The term evolution is derived from two Latin words and means the act of unfolding or unrolling. English philosopher Herbert Spencer first used it. Evolution is defined as the change in heritable traits of biological populations over successive generations. These traits are the manifestations of genes that are passed down from parent to offspring during reproduction.
Cladistics
Cladistics is a technique in the classification of organisms, where they are grouped into different clades. The proof for the relationships that are hypothesized is based on the shared derived characteristics known as synapomorphies. These characteristics do not exist in many of the distant ancestors and groups. The common ancestor along with its descendants is considered to be a part of the clade. The rate of closeness is directly proportional to the cladistic grouping and is useful in analyzing the evolutionary mechanism.
Outgroups
Outgroups are significant in studying cladistics or phylogenetics (that describe the evolutionary relationship between different organisms). Further, it is also important to understand the differences and similarities between different organisms.
Taxonomy
It is the branch of biology that works with the identification of organisms at first, then naming, and classification of them into phenetic or phylogenetic groups (a classification system). In other words, it is the scientific study of biological diversity and a part of systematic biology.
Phylogenetics
Phylogenetics is the scientific study of how various groups of organisms are related at the evolutionary level. It finds the relationship between various organisms based on their evolutionary similarities and differences. It is a part of the taxonomy. Although the taxonomic study is not only concerned about phylogeny but taxonomic studies are also concerned about the classification and nomenclature of the different individuals from different taxon.
Explain how whole muscles respond in a graded fashion
and how the force of contraction can be increased
At the neuromuscular junction, the location where the motor neuron binds to the muscle, force in the skeletal muscles is graded by regulating the strength of the firing of impulses. A difference in muscle tension is often enabled by a graded muscle response.
A single reaction to a specific stimulus is a muscle twitch. Due to the form of muscle cells engaged, muscle twitches differ in duration. There are fast-twitch muscles like those that drive the eyeball that achieves full contraction in 3 to 5 milliseconds (ms). Cells like the postural muscles (for example, back muscles) are classified as slow-twitch muscles that have twitches that achieve maximal stress in approximately 40 ms.
As part of ordinary muscle reactions, these muscle twitches are not used. Graded contractions, contractions of whole muscles that may differ in strength and intensity of contraction, are used in twitches instead. In addition, even relaxed muscles are continuously activated to create a muscle tone, the minimum possible graded contraction.
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