The embryo has all the basic organs and body parts (except male and female organs) at approximately how many weeks after conception

After the completion of first trimester that is 8 weeks of conception, the baby is almost 1 inch grown. At this stage, the baby is referred as fetus. At this stage, all the organs as well as limbs becomes visible except for the sex organs.

The heart of baby beats rhythmically. Eyes and the eyelids are completely visible. Both the forelimbs and the hind limbs are formed, and fingers buds are also visible.

At this stage, the fetus looks like a human. The umbilical cord is also clearly visible at this stage.

Hence, the correct answer is 8th week.

answer: tributaries flow into rivers.

wetland is a biome that develops when the water gets accumulated in a land exhibiting a huge depression. these form either seasonally or permanently. the water in the wetland comes from rivers, lakes, ocean, flood, rain or other sources. the wetlands includes mangroves, marshes and peatland.

tributaries flow into the rivers develops a wetland because such water will get deposited in the depression and will restrict the original flow of tributary water. hence, water with low drainage current combines with the river water.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".