የባዮሎጂ መግቢያ ፈተና፣ 2013 ዓ.ም. (2021)

Lucy is a fossil of Australopithecus afarensis found in Ethiopia in 1974. Her leg, pelvis and spine show that she walked upright on two legs, yet her brain was still small, close to the size of a chimpanzee's brain.

Before her discovery, scientists argued about which came first: a big brain or upright walking. Lucy settled that debate. Bipedalism came before big brains, so option C is correct.

Textbook: Biology Grade 12, Unit 4 Evolution, section 4.1.5 Human evolution (page 200).

In biology, behavior is the coordinated response of an organism to internal or external stimuli. The word "organism" matters here: all living things behave, not only people and animals. Plants also respond to stimuli, for example by growing toward light.

Option C is tempting, but it limits behavior to persons and animals, so it is too narrow. Option B is only one plant example, and option D defines a receptor, not behavior.

Textbook: Biology Grade 11, Unit 2 Animals, section 2.5 Animal behavior.

Pulling your hand away from a hot plate is a simple reflex: a sudden, involuntary response that does not have to be learned. Reflexes belong to innate (inborn) behavior, so B is correct.

A fixed action pattern is a complete sequence of instinctive actions, such as web building in spiders, not a single quick response. A biological clock controls repeating rhythms, and a key stimulus is the trigger of a behavior, not the behavior itself.

Textbook: Biology Grade 11, Unit 2 Animals, section 2.5.1 Types of animal behavior.

A biological clock is an internal timer that makes a behavior repeat on a regular cycle. Bird migration from temperate to tropical areas happens once every year, on a yearly rhythm called a circannual rhythm, so it is driven by a biological clock.

Hand withdrawal is a reflex, growth toward light is a plant tropism, and kinesis and taxis are simple orientation movements. None of these run on a timed cycle.

Textbook: Biology Grade 11, Unit 2 Animals, section 2.5.2 Patterns of behavior.

Learned behavior is gained through experience or training during an animal's own life. A dog hunts on command only because a person trained it, so this is learned behavior.

Making honey, pulling a hand away from heat and building nests are inborn abilities. The animals do them correctly the first time, without any training, so they are innate.

Textbook: Biology Grade 11, Unit 2 Animals, section 2.5.1 Types of animal behavior.

Bacteria are prokaryotes. Their DNA lies free in the cytoplasm because there is no nuclear membrane around it. Among the choices, this is the feature that separates bacteria from eukaryotic cells.

The other options are shared with many organisms: every cell has a selectively permeable membrane, protozoa and some algae are also unicellular, and sperm cells and many protists also move with flagella.

Textbook: Biology Grade 12, Unit 2 Microorganisms, section 2.1 Eubacteria (page 43).