Paul baltes believes that natural selection has not weeded out many harmful conditions and nonadaptive characteristics that appear among older adults because those conditions are not tied to

Reproductive fitness.

Explanation:

The natural selection may be defined as one of the most important factors that plays the main role in evolution. Darwin explains the theory of the natural selection.

The organisms must adapt to their environment and reproduce in the large numbers. The reproductive fitness  helps the individual to effectively transfer their genes to the next generation. The successfully adapted and evolved population must show high reproductive fitness. The natural selection increase the chance of individual to survive in harmful environmental conditions and do not remove the conditions.

Thus, the answer is reproductive fitness.

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explanation:

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estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.