Natural selection.
Genetic engineering.
Geographic isolation.
Reproductive isolation.
Ecological competition.
Movement in and out of populations.
There're A LOT more reasons.
Some animals mutate creating adaptations that make them more successful than other animals. through these adaptations natural selection weeds out the least adaptive to change and thus you have some animals more healthier, stronger and smarter than others.
It is because of their genes and their species. Some animals have smaller brains than others, there for, some have more abilities and are more curious. By being curious, the animal will be more experienced and be smarter.
yes yes
all animals are equal but some are more equal than others
Protists are actually not animals; they are a diverse group of eukaryotic organisms that are not plants, fungi, or animals. They can be unicellular or multicellular, and they are known for their diverse habitats and modes of nutrition. Some protists are capable of photosynthesis, while others are heterotrophic.
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Some animals need better senses because they may have more predators or prey.
"All animals are equal, but some animals are more equal than others"
The irritability of animals is called temperament. As in dog breeds, some are gentle and others have a more profound territorial instinct.
To increase the chance of it being fertilised
all the plant and animals depend on the water cycle some more than others
Because some of their pelts (or fur) are more beautiful than others. Therefor they are worth more causing people to kill them so they can make money.