An ecosystem<span> is </span>balanced<span> when the natural animals and plants and non-living components are in harmony- i.e. there is nothing to disturb the </span>balance<span>. With increasing pollution, change in migratory patterns, and rise of human population, many </span>ecosystems<span> are in danger of losing that harmony.</span>
Interphase:
-the cell replicates its chromosomes
-each chromosome has two sister chromatids held together by a centromere
Prophase 1 chromosomes coil up and a spindle forms
-homologous chromosomes come together matched gene by gene forming a tetrad
-Crossing Over may occur when chromatids exchange genetic material
-this occurs two or three times per pair of homologous chromosomes
-Crossing Over results in new combinations of alleles on a chromosomes
Metaphase 1:
-the centromere of each chromosome becomes attached to a spindle fiber
-the spindle fibers pull the tetrads to the equator of the spindle
-homologous chromosomes are lined up side by side as tetrads
Anaphase 1:
-homologous chromosomes separate and move to opposite ends of the cell
-centromeres do not split
-this ensures that each new cell will receive only one chromosome from each homologous
pair
Telophase 1:
-the spindle breaks down and the chromosomes uncoil
-the cytoplasm divides to yield two new cells
-each cell has half the genetic information of the original cell because it has only one homologous
chromosome from each pair
Prophase II-
-a spindle forms in each of the two new cells and the fibers attach to the chromosomes
Metaphase II-
-the chromosomes are pulled to the center of the cell and line up randomly at the equator
Anaphase II-
-the centromere of each chromosome splits the sister chromatids separate and move to opposite poles
Telophase II nuclei re form the spindles break down the cytoplasm divides identical to mitosis (Meiosis II)
What Meiosis produces four haploid sex cells from one original diploid cell each haploid cell contains one chromosome from each homologous pair haploid cells will become gametes transmitting genes to offspring
I hope this helps
Answer:
c. Cardiac muscle contains bands like skeletal muscle, but its contractions are involuntary like smooth muscle.
Explanation:
In Human anatomy, cardiac cycle can be defined as a complete heartbeat of the human heart which comprises of sequential alternating contraction and relaxation of the atria and ventricles, therefore causing blood to flow unidirectionally (one direction) throughout the human body.
Cardiac muscle is also referred to as myocardium and it's one of the three (3) muscles found only in the heart of vertebrates, the other two (2) being smooth muscle tissue and skeletal muscle tissue.
Cardiac muscle contains bands like skeletal muscle referred to as sarcomeres (contractile units), but its contractions are involuntary like smooth muscle and it's typically being regulated by the sinoatrial node of the heart.
<span>There are numerous proteins in muscle. The main two are thin actin filaments and thick myosin filaments. Thin filaments form a scaffold that thick filaments crawl up. There are many regulatory proteins such as troponin I, troponin C, and tropomyosin. There are also proteins that stabilize the cells and anchor the filaments to other cellular structures. A prime example of this is dystrophin. This protein is thought to stabilize the cell membrane during contraction and prevent it from breaking. Those who lack completely lack dystrophin have a disorder known as Duchene muscular dystrophy. This disease is characterized by muscle wasting begininng in at a young age and usually results in death by the mid 20s. The sarcomere is the repeating unit of skeletal muscle.
Muscle cells contract by interactions of myosin heads on thick filament with actin monomers on thin filament. The myosin heads bind tightly to actin monomers until ATP binds to the myosin. This causes the release of the myosin head, which subsequently swings foward and associates with an actin monomer further up the thin filament. Hydrolysis and of ATP and the release of ADP and a phosphate allows the mysosin head to pull the thick filament up the thin filament. There are roughly 500 myosin heads on each thick filament and when they repeatedly move up the thin filament, the muscle contracts. There are many regulatory proteins of this contraction. For example, troponin I, troponin C, and tropomyosin form a regulatory switch that blocks myosin heads from binding to actin monomers until a nerve impulse stimulates an influx of calcium. This causes the switch to allow the myosin to bind to the actin and allows the muscle to contract. </span><span>
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