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Schach [20]
3 years ago
15

Which statement describes many of the structures involved in the first line of defense of the immune system? They have contact w

ith the external environment. They are internal and contact the pathogen through blood. They produce B-cells in response to a pathogen. They produce T-cells in response to a pathogen.
Biology
2 answers:
Strike441 [17]3 years ago
6 0

Answer:

The correct answer would be They have contact with the external environment.  

The first line of defense refers to the outside defense system which consists of physical and chemical barriers.

They have contact with the external environment and help in preventing the entry of the infectious agent in the body.

They include skin, mucous membranes and their secretions such as tears, stomach acid, urine flow, et cetera.

cricket20 [7]3 years ago
4 0
They have contact with the external environment.
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Keratinocytes are differentiated skin cells found in the outermost layer of the epidermis. Dendritic cells are antigen-presenting cells that play important roles in the adaptive immune response.

  • In addition to keratinocytes, the <em>stratum spinosum</em> also contains another epidermal cell type called epidermal DENDRITIC cells that help to fight infection.

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2 years ago
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12. The more genetic variation a population has, the
AveGali [126]

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b migrate

Explanation:

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4 0
3 years ago
At the molecular level, gene duplication often produces novelty in a lineage. This process provides another evolutionary pathway
alukav5142 [94]

Answer:

Bridgham et al. (2006) showed that the interaction between a steroid hormone (aldosterone-M) and its receptor (mineralocorticoid) evolved by Darwinian gradualism. In this work, the authors demonstrated  a primitive affinity between the hormone and its receptor that was initially present in chemically similar but more ancient ligands. This result has implications in understanding the association between gene duplication and the evolution of hormone signaling pathways. For example, in invertebrates, this work reinforces the importance of gene duplication in the existing interaction between paralogous glucocorticoid receptors and their receptor mineralocorticoid genes that were derived from duplication (Thornton 2001).

The publications above cited are the following:

J.T. Bridgham, S.M. Carroll, and J.W. Thornton (2006). Evolution of hormone-receptor complexity by molecular exploitation. Science, 312(5770), 97-101.

JW Thornton. Evolution of vertebrate steroid receptors from an ancestral estrogen receptor by ligand exploitation and serial genome expansions, Proc Natl Acad Sci USA (PNAS), 2001, vol. 98 10 (pg. 5671-5676).

6 0
3 years ago
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Bacteria, archaea, plants, protists, animals, and fungi, can use cellular respiration.

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Hope I helped you out (:

4 0
3 years ago
Read 2 more answers
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