The prenatal circulation of blood is different than the postnatal circulation, mainly because the lungs are not in use. The fetus obtains oxygen and nutrients from the mother through the placenta and the umbilical cord. Blood from the placenta is carried to the fetus by the umbilical vein.
Answer:
Herd immunity
Explanation:
Herd immunity refers to the resistance of a group of people against infection and the spread of a pathogen. It occurs when a high proportion of the members of that group are resistant against a particular pathogenic infection. When an earlier exposure or vaccination of a large proportion of individuals of a population does not allow the pathogen to spread among and infect the otherwise susceptible members of the population, the population is said to have acquired the herd immunity.
In the given example, vaccination of a large percentage of a population protected the susceptible individuals against a particular microbe. This represents an example of herd immunity.
Explanation:
Fertilization, pictured in Figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. The egg and sperm each contain one set of chromosomes. To ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. In mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. When a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. In placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in Figure 24.23b. The fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. The nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.
Answer:
Solar energy warms gases that make up air
Answer: The four kingdoms of Eukarya are: <em>Animalia</em> (Metazoa), <em>Plantae</em>, <em>Fungi</em>, and<em> Protista.
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1) <u>Animalia: </u>
- They are multicellular organisms that do not possess chlorophyll!
- They are eukaryotic organisms!
2) <u>Plantae:</u>
- They are multicellular organisms with walled and frequently vacuolate eukaryotic cells!
- These contain photosynthetic pigment in plastics!
3) <u>Fungi:</u>
- Fungi are eukaryotic organisms means they have a true nucleus which is enclosed in membranes.
- They are non-vascular organisms!
4) <u>Protista:</u>
- Protists have a nucleus containing their DNA.
- They also have other membrane-bound organelles, such as mitochondria and the endoplasmic reticulum!
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