Natural Selection vs. Selective Breeding

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7th Grade Science

Selective Breeding

• SELECTIVE BREEDING is the process of choosing parent organisms for the characteristics that we want in their offspring.

• Who plays a large role in this process? We do,

as HUMANS! ☺

Selective Breeding Examples

• MATING male and female English BULLDOGS that exhibit characteristics and selling their OFFSPRING.

• Farmers choosing the TRAIT they want from the CROP to breed.

• SELECTIVE BREEDING can include ranchers breeding cows and buffalo to get a certain kind of meat.

It Gets Lonely in the Desert

• To survive in the desert, plants must adapt to their environment. This can include: • Having short roots• Waxy coats on their leaves

• Some desert plants bloom only at night because the SPECIES RELIES ON NOCTURNAL ANIMALS FOR POLLINATION.

Adapt, Adapt, Adapt!

• PLANTS and ANIMALS are two types of organisms that adapt to their environments.

• Adaptations helps species SURVIVE and REPRODUCE in their ENVIRONMENT.

• Adaptations often evolve from a MUTATION and gave the species an ADVANTAGE.

Adapt, Adapt, Adapt!

• Adaptations occur OVER TIME and can be PHYSICAL or BEHAVIORAL.

• Adaptations must be common amongst a POPULATION. They CANNOT occur in just a single INDIVIDUAL.

• To avoid predators, an organism might CAMOUFLAGE COLORING, LIVE IN GROUPS, and have SENSITIVE HEARING.

Adapt, Adapt, Adapt!

• If body temperature rises, the adaptive response would be to SWEAT.

• To survive in cold weather, humans must keep warm! One human adaptation to survive in cold weather is to GROW HAIR TO INSULATE THE HEAD.

Adapt, Adapt, Adapt!

• CAMOUFLAGE is an example of an adaptation. The SNOWSHOE HARE changes its color from brown to white to blend into the snow during winter.

• One adaptation of dandelions is that they are attached to stems with light, fluffy threads. This helps them DISPERSE SEEDS VIA THE WIND.

Let’s Eat!

• What do you like to eat???• Some animals, like SHARKS have very SHARP teeth

to eat only MEAT.

• Deer are herbivores, so their teeth are more FLAT to chew leaves or plants.

• Humans are OMNIVORES, so they have both.

Natural Selection—Charles Darwin

• CHARLES DARWIN’S theory of natural selection stated that individual that tend to survive have VARIATIONS BEST SUITED FOR THAT ENVIRONMENT.

• Darwin studied the FINCHES on the Galapagos Islands. He noticed they had different BEAKS. They formed so the birds could EAT DIFFERENT FOODS.

Natural Selection

• NATURAL SELECTION is the process that leads to the most VARIATIONS.

• The Peppered Moth had a change in population caused by NATURAL SELECTION.

• Natural selection is NOT the survival of the STRONGEST and BIGGEST organisms in a population.

Homeostasis

• HOMEOSTASIS is the process of trying to maintain an internal stable environment despite an ever-changing external environment.

• As humans, our bodies use mostly NEGATIVE feedback to maintain stability, or homeostasis.

Homeostasis

• Positive feedback tends to be more RARE. An example of positive feedback would be APPLES RIPENING ON A TREE.

• When apples ripen, they give off a gas called ETHLENE which causes other surrounding apples to ripen as well.

Homeostasis

Example Positive Feedback Negative Feedback

Apples Ripening X

Thermostat/AC X

Breastfeeding X

Oxygen levels in the body X

Blood sugar levels in the body X

Shivering X

Key TermsAdaptation A structure, behavior, or other trait in an organism that

helps it survive in its environment

Variation A property of a population that occurs when individuals within a population differ in the characteristics

Natural Selection Survival and reproduction of the organisms that are genetically best adapted to the environment

Homeostasis The process by which an organisms’ internal environment is kept in equilibrium, or stable in spite of changes in the external environment

Selective Breeding The process of choosing parent organisms for the characteristics that we want in their offspring