Songs for birds give them a communication system so that they can alert other birds and also to attract mates.
Answer:
4) action stage
Explanation:
The Stages of Change Model is based on the premise that people change their behavior gradually and continuously. They start from the complete lack of awareness of the need for change, make the decision to change, and exercise the new conduct until it becomes a habit. This behavior change process is divided into five successive stages of change. The stage at which one finally changes one's behavior is called the action stage.
It is only at the action stage that Adam will stop smoking. This is because it is at this stage that changes are made to a person's behavior.
Well, this question cannot really be answered generally. It's a matter of judgement, and it's best judged for particular cases. The consideration of this depends on two factors:
what are the probable costs (in terms of human life, and the quality of human life) of the invasion? - it's important not to diminish these factors, as the assessments of casualties often tend to be lower than the actual numbers
how high is the risk of the alternative. Do we have a good, unbiased reason to believe that a spread of nuclear weapons (unchecked spread, or spread that gives reasons to worry. US has a lot of nuclear weapons, but since it's not planning to use them on other country, it wouldn't be justified to attach the US) will happen? what kind of conflict are we risking?
in any case, this is not an easy question, and perhaps there will never be a good answer for it.
The first settlement of the Americas began when Paleolithic hunter-gatherers first entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the Last Glacial Maximum. These populations expanded south of the Laurentide Ice Sheet and rapidly throughout both North and South America, by 14,000 years ago.[1][2][3][4] The earliest populations in the Americas, before roughly 10,000 years ago, are known as Paleo-Indians.
The peopling of the Americas is a long-standing open question, and while advances in archaeology, Pleistocene geology, physical anthropology, and DNA analysis have shed progressively more light on the subject, significant questions remain unresolved.[5] While there is general agreement that the Americas were first settled from Asia, the pattern of migration, its timing, and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear.[2] In 2019, a study by the University of Cambridge and University of Copenhagen concluded that Native Americans are the closest relatives to the 10,000-year-old inhabitants of the Kolyma River in northeastern Siberia.[6]
The prevalent migration models outline different time frames for the Asian migration from the Bering Straits and subsequent dispersal of the founding population throughout the continent.[7] Indigenous peoples of the Americas have been linked to Siberian populations by linguistic factors, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.[8]
The "Clovis first theory" refers to the 1950s hypothesis that the Clovis culture represents the earliest human presence in the Americas, beginning about 13,000 years ago; evidence of pre-Clovis cultures has accumulated since 2000, pushing back the possible date of the first peopling of the Americas to about 13,200–15,500 years ago.
