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Biology Chapter 16


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Chimpanzees live in family groups with male-kin societies where females are forced to leave the group once reaching adulthood, a social structure known as a __________ society.
Humans and chimpanzees have genomes of nearly the same size and share DNA sequences similarity of __________%.
The earliest fossils with human-like feature date back to __________ million years ago.
The discovery of Lucy, a fossil nearly 4 million years old, showed the first time at which human-like ancestors walked upright, a type of locomotion known as __________.
The most widely accepted hypothesis for the evolution of bipedalism is the __________ hypothesis.
Research has shown that at least __________ different human species evolved and then went extinct.
The first human species to leave Africa was Homo __________.
As a result of an ice age 500,000 years ago, the population of humans in the North (Europe) evolved into the __________.
As a result of an ice age 500,000 years ago, the population of humans in the South (Africa) evolved into __________.
Homo sapiens
Due to a drought in Africa 120,000 years ago, the entire Homo sapien population was reduced to less than __________ individuals.
The phenomenon in which an entire population is the descendants of only a few individuals is known as a genetic __________.
The discovery of the human genetic bottleneck was made by studying human __________ DNA.
Every modern human evolved from a small group of Homo sapiens that originated on the continent of __________.
When comparing the genomes of any two humans from any part of the world, their DNA sequences are __________% identical.
The hypothesis that suggests that modern Homo sapiens left Africa and out competed all other human species to extinction is the __________ Model.
Out of Africa or Replacement
The hypothesis that suggest that local population evolved into humans and subsequent interbreeding with African migrants led to the genetic homogeneity of modern humans is known as the __________ Model.
Multi-Regional Evolution
Describe the complex patrilocal society of the common chimpanzee.
Chimpanzee society is very male dominated. All of the males in a family group are related because males remain with the same family group as adults. They have a strong kinship with one another. Females, however, do not remain with the family group they were born into. At adulthood they must leave that family group and find another to join. This type of society is biologically advantageous in that it prevents inbreeding.
How does chimpanzee tool usage demonstrate the existence of chimpanzee culture?
While all chimpanzee groups use simple tools, such as sticks to retrieve termites and stones to crack nuts, how they used them to do these things varies between family groups. This shows that tool usage is a learned technique passed on from adult to young, an example of a cultural aspect of their society.
How did the ice age of 500,000 years ago and the resulting drought in Africa ultimately result the evolution of Homo sapiens?
There were two groups of human ancestors (Homo heidelbergensis), one living in Europe and the other in Africa at the time of an ice age 500,000 years ago, that were separated by the resulting drought. The two groups evolved along different lines, with the European group becoming neandertals, while the group in Africa evolved on a different pathway and eventually became Homo sapiens.
What is a genetic bottleneck and how do we know that one occurred to the Homo sapien population?
A genetic bottleneck is a phenomenon where for some reason, possibly environmental change, a group of organisms is forced nearly to extinction. The very small population size results in inbreeding. This inbreeding then results in a decrease in the genetic diversity of the surviving population. By studying mitochondrial DNA, we now know that the human population was at one point decreased to less than 10,000 individuals.
Explain the 2 theories for why Homo sapiens are the only remaining human species and tell which one is the more likely of the 2 and why.
The Replacement Model or Out of Africa Model states that when Homo sapiens evolved and left Africa, they spread out into the territory of other human species and out competed them for the available resources. The other human species could no longer find enough food to survive and thus became extinct, leaving only Homo sapiens. The other theory, known as the Regional Continuity Model or Multi-Regional Evolution ModelS states that Homo sapiens spread out from Africa and interbred with the other existing species so thoroughly that eventually there was only one human species. The Replacement or Out of Africa Model is the favored theory because the very high similarity of genome sequences between all existing humans suggests that there wasn’t significant interbreeding and that we all came from one species, the Homo sapiens that drove the other human species to extinction.

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