Answer:
Explanation:
Sister chromatids are regarded as replicated chromosomes. Sister chromatids are two identical copies of chromosomes held at the centromere that are formed as a result of replication. They are identical in the sense that they contain same alleles/gene sequence of the same genes. 
Homologous chromosomes, on the other hand, are similar (in length, centromere position) but non-identical chromosomes. Homologous are non-identical in the sense that they may contain different alleles of a gene and are received from each parent. homologous chromosome contain four chromatids; two of which are sister chromatids and non-sister to the other two.
Both undergo meiosis where homologous chromosomes separate in meiosis I while sister chromatids separate in meiosis II but only sister chromatids undergo mitosis.
 
        
                    
             
        
        
        
Answer:
A snail eats a clam.
Explanation:
Interactions always occur between organisms in an ecosystem. An interaction between two organisms is called SYMBIOSIS. Symbiosis consists other types which includes PREDATION. Predation is a kind of symbiotic relationship between two organisms in which one kills and feeds on the other in order to obtain energy. The organism that kills is called the PREDATOR while the organism that is killed is called PREY.
In this example, a snail feeding on a clam best represents the example because the snail (PREDATOR) is obtaining energy by killing the clam (PREY). In other options, no organism is killed.
 
        
             
        
        
        
Answer:
The placenta is a unique vascular organ that receives blood supplies from both the maternal and the fetal systems and thus has two separate circulatory systems for blood: (1) the maternal-placental (uteroplacental) blood circulation, and (2) the fetal-placental (fetoplacental) blood circulation. The uteroplacental circulation starts with the maternal blood flow into the intervillous space through decidual spiral arteries. Exchange of oxygen and nutrients take place as the maternal blood flows around terminal villi in the intervillous space. The in-flowing maternal arterial blood pushes deoxygenated blood into the endometrial and then uterine veins back to the maternal circulation. The fetal-placental circulation allows the umbilical arteries
Explanation: