Natural Selection Notes

Natural Selection

• The process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well-adapted individuals do.

Four Parts of Natural Selection1. Overproduction – More offspring are born

than will live to be adults2. Genetic Variation Within a Population – The

individuals are different. Some characteristics increase chances of survival.

3. Struggle to Survive – Competition for water, food, and mates; predators

4. Successful Reproduction – Key to natural selection – Organisms that are best adapted to their environment survive and reproduce and pass on their “good traits”

Changes in Genetic Variation

• If a population loses many members rapidly, genetic variation is lost making the population more susceptible to disease and birth defects.

Florida Panther Population• Because of isolation from other populations of

panthers, habitat loss, and overall decrease in population size, the genetic variation within this group has decreased.

• Many surviving panthers have become genetically similar causing inbreeding within the population.

• The results have been: heart defects, failure of reproductive organs, and low birth rates

• A recovery program has been implemented.

Insecticide Resistance

• When insecticides are applied, some organisms are not killed.

• These surviving organisms develop an immunity to the chemicals which is passed on to their offspring.

Antibiotic Resistance•Occurs when bacteria is not killed by an antibiotic treatment and the bacteria mutates•This resistance to a particular antibiotic is passed from parent bacteria to offspring.•Since bacteria reproduces asexually by fission which only involves one parent, one bacterium can become 2 million in 7 hours.

Why have some bacteria become antibiotic resistant?

• Antibiotics taken when they are not really necessary

• Not following the doctors’ antibiotic directions properly

• Overusing antibacterial soaps, lotions, etc.

Reproduction in AnimalsAsexual Reproduction• Allows for no genetic variation• ALL genetic information comes from the ONE

parent • Allows for many offspring in a short amount of

time• Methods:– Budding (hydra)– Fragmentation (starfish)

Budding Hydra

Budding Yeast

Starfish

Sexual Reproduction• Forms offspring that are combinations of

genetic material from two different parents• Female parent supplies the egg• Male parent supplies the sperm• When the egg and sperm unite, fertilization

occurs and the zygote is formed

Fertilization of Egg

• Genetic information is found on genes (which are located on chromosomes, made of DNA and proteins)

• Allows for great amounts of genetic variation

Chromosomes and DNA

Internal or External??

• Sexual reproduction can occur by:– External Fertilization• Requires a moist environment to prevent zygote from

drying out• Fish and many amphibians release eggs (female) and

sperm (males) into the water where they unite

– Internal Fertilization• Egg and sperm join inside the mother’s body• Allows the female to protect the developing zygote

inside her body• Reptiles, birds, and some fishes then lay the fertilized

eggs and development continues outside of the mother• Development of the zygote continues inside the mother

of most mammals

Groups of Mammals

• Monotremes – Egg layers; Echidnas and platypus• Marsupials – Mammals whose young complete

development inside a pouch that is outside the uterus of the mother; examples -opossum, kangaroos, koalas, wombats, and Tasmanian devils

• Placental Mammals – Nourished inside the mother’s body before birth and are more developed than monotremes or marsupials; over 4000 species

Long-Beaked Echidna

Platypus

Short-beaked Echidna

Marsupials

Placental Mammals

Reproduction in Plants

• Nonvascular Plants– Examples – mosses, liverworts, and hornworts– Gametophytes of these plants must be covered by

a film of water so sperm can swim to the eggs for fertilization to occur

Moss

Liverworts

Hornworts

• Seedless Vascular Plants– Vascular plants have tissues that deliver materials

from one part of the plant to another– Produce a lot of spores– Require water to reproduce– Many plants produce both eggs and sperm– Gametophytes are very small and develop on or

below the surface of the soil

Seedless Vascular Plants - Ferns

Horsetails

• Seed plant reproduction– Gymnosperms• Reproductive structures called cones• Have male and female cones• Male gametophytes = pollen (contains sperm)• Female gametophytes produce eggs• Wind transfers pollen so that fertilization occurs.• Seeds form from fertilized eggs

Gymnosperms

– Angiosperms• Gametophytes are within flowers• Anthers (male reproductive structure)• Stigmas (female reproductive structure)• Pollination – pollen is moved from the anthers to

stigmas• Wind or animals usually help move pollen• Pollen lands on the stigma then a tube forms allowing

the pollen to travel to an ovule to fertilize it

Angiosperms

• From flower to Fruit– After fertilization, the ovule develops into a seed (contains

young plant)– Ovary, which surrounds the ovule, becomes a fruit (which

protects the seed)– Seeds are dispersed by wind, animals eating the fruit (and

seeds) and releasing them in other places as wastes, or getting caught in the animal’s fur (such as burrs)

– From Seed to Plant• To sprout, most plants need:

– Water– Air– Warm temperatures

Asexual Reproduction in Plants

• Plantlets– Tiny plants grow along the edges of a plant’s

leaves• Tubers– Underground stems (Example – Potato)

• Runners– Above ground stems (Example – Strawberry)

Plantlets

Tubers

Runners

Animal Behavior

Kinds of Behavior• Innate – Does not depend on learning or experience– Inherited through genes– The male bowerbird inherits the tendency to

collect colorful objects for its nest.– Puppies inherit the tendency to chew– Bees inherit the tendency to fly– Whales to swim– Some innate behaviors take time to develop

(Walking in humans)

Kinds of Behavior (Cont’d)

• Learned Behavior– Has been gathered through experience or

observation– Innate behaviors can be modified through learning– Humans inherit the tendency to speak, but the

language we use is learned.

Survival Behavior

• Finding Food– Bees flying from flower to flower– Koala bears climbing to get Eucalyptus leaves– Chimpanzees using tools– Hunting– Animals that eat other animals are predators. The

animal being eaten is the prey.– Frog Insects; Snake Frog

Survival Behavior (Cont’d)

• Marking Territory– Claiming territory cuts down energy spent on

competing for food– Marking territories helps with mating, raising

young, and food.– Birds sometimes mark their territory by the song

they are singing.

Survival Behavior (Cont’d)

• Defensive Action– Animals defend food, mates, and offspring.– They may fight or distract to defend.– Blending into the environment is a method of

defense.– Outrunning predators– Chemical defense

Survival Behavior (Cont’d)

• Courtship– Help in finding mate– Some birds and fish build nests to attract a mate– Special movements (or courtship “dances”)

Survival Behavior (Cont’d)

• Parenting– Caterpillars begin life able to take care of

themselves– Many young animals, however, depend on their

parents for survival– Birds bring food to their young; killer whales

spend years teaching their young to hunt for food.

Seasonal Behavior• Migration– Moving to avoid undesirable weather conditions

to find food, water, or safe nesting grounds– Whales, salmon, bats, and even chimpanzees are

migratory animals– Monarch Butterflies migrate from North America

to Mexico for warmer condition.– Migratory animals use landmarks (Mountain

ranges, rivers, and coastlines) to help them find their way.

Seasonal Behavior (Cont’d)

• Slowing Down– Hibernation – period of inactivity and decreased

body temperature, heart rate, and breathing that some animals experience in winter. • Survive on stored body fat

– Estivation – period of reduced activity during the summer• Examples - Desert Squirrels and Mice

Biological Clock

• Internal control of an animal’s natural cycles• May use clues such as day length and

temperature to set their clocks• Circadian Rhythms – Daily cycles

Adaptations and Survival

• Adaptation – characteristic that improves an individual’s ability to survive and reproduce in a particular environment.

Adaptations for Obtaining Food

• Chameleon – long, fast-moving tongue to catch insects

• Woodpecker – strong, sharply-pointed beak for drilling into trees

• Humans – shape and function of our hands and fingers helps to pick and peel fruit and open jars

Predator-Prey Adaptations

• Porcupine – Protective covering• Coral snake – Bright markings to warn

predators• Bees, wasps, skunks, snakes, and poisonous

frogs – warning colors• Camouflage – animal disguised to blend in

with surroundings

Adaptations to Interactions

• Mutualistic Relationship – Honeycreeper has a long, curved beak which allows it to reach in to Lobelia flower to get nectar. The bird then transfers pollen to a different flower. (Bird gets food – flower gets pollinated.)