CHAPTER 2 LESSON 1

REPRODUCTION

WHERE DO LIVING THINGS COME FROM?

•Living things come from other living things. •Every organism comes from a parent organism through the process of reproduction.

REPRODUCTION

• Reproduction involves the transfer of genetic material from parent to offspring. • The genetic material contains information that controls how the new organism will look and function.

TWO MAIN TYPES OF REPRODUCTION

•Sexual reproduction is the production of a new organism from two parents.

•Asexual Reproduction is the production of a new organism from a single parent.

SEXUAL REPRODUCTION

• Fertilization: The process where a sperm cell from a male and an egg cell from a female join into a single unit.• Genetic material from both parents is contained

in a fertilized egg. This egg will grow an develop into a new individual that will have characteristics from both parents. • Trait: any characteristic of a living thing. An

example of a trait is the height of a plant and the color of flowers the plant produces is a trait passed on from parent plants.

ASEXUAL REPRODUCTION

• Single parent• Produces new offspring with the same genetic

information as the parent. The offspring are IDENTICAL to the parent.

• All six kingdoms have organisms that reproduce asexually.

• Bacteria, archaea, most fungi, plants can reproduce asexually.

• Examples of animals that can reproduce asexually are: jellyfish, corals, worms, and echinoderms. Also, some lizards, frogs, fish and insects reproduce this way.

REVIEW

•What type of reproduction involves only one parent?• Asexual reproduction•Which type of reproduction requires fertilization?• Sexual reproduction

HOW DO ORGANISMS REPRODUCE ASEXUALLY

• Asexual reproduction produce genetic copies of the parent organism.

• Splitting: Most unicellular protists and bacteria reproduce by splitting into two cells. The organism copies its own genetic material.

• Budding: Cnidarians, sponges, and some fungi reproduce through budding. A small part of the parent’s body grows into a tiny and complete version of the parent. The bud can break off from the parent and continue to grow or it can remain attached to the parent as in coral.

ASEXUAL REPRODUCTION

• Some fish, insects, frogs, and lizards go through asexual reproduction. Egg cells are produced by the females and sometimes fertilization does not take place. The eggs develop into a new animal without fertilization.

• Examples: Honeybees lay eggs. Some get fertilized and some do not. The ones that get fertilized develop into females or worker bees. The ones that are not fertilized develop into males or drone bees.

ASEXUAL REPRODUCTION: PROPAGATION

• Vegetative Propagation is a form of asexual reproduction in plants that produces new plants from leaves, roots, or stems. • Runners are plant stems that lie on or under the

ground and sprout up as new plants. • Examples: Strawberry plants, aspen tree, ferns

and most grasses

WHAT ARE SOME DIFFERENT KINDS OF ASEXUAL REPRODUCTION?

• Splitting• budding• developing from unfertilized eggs• vegetative propagation

• http://mrsdlovesscience.com/asexualrepro.html

LOOK AT THE IMAGES OF SPLITTING AND BUDDING

• What is the most important difference between the processes?• Splitting occurs as single-celled organisms split

into two cells. Budding involves a small part of the parent’s body that grows into a new individual.

REVIEW

• What is the difference between a drone and a worker bee?• A drone is a male bee and develops from an

unfertilized egg. A worker bee is female and develops from a fertilized egg.

WHAT PART OF THE STRAWBERRY PLANT CAN PRODUCE NEW PLANTS WITHOUT SEEDS?

•The stem

SEXUAL REPRODUCTION

•When plants and animals reproduce sexually, a fertilized egg develops into the embryo. •An embryo is the beginning of a new offspring

SEXUAL REPRODUCTION IN PLANTS

• Many plants reproduce sexually and the reproductive structures for these are often flowers.

• Inside the ovary of a flower, fertilization takes place. The inside of the seed is where the embryo grows. This seeds contains all the food supply for the growing embryo. Eventually the embryo will develop enough to make its own food.

• Fruit develops from the ovary and it protects the seed inside. Another form of protection comes from the seed coat which is tough outer covering.

SEXUAL REPRODUCTION IN PLANTS

• Plants can have seeds that are not inside of fruit and don’t have flowers. They use cones for reproduction.• These plants are called conifers and

fertilization takes place inside the cone. After fertilization, the developing egg matures into a seed inside the cone.• Seeds must be dispersed (spread) to

a location where the seed can germinate or sprout. • Germination is the sprouting of a

seed as it develops into a new plant.

SEED DISPERSAL

• Seeds are dispersed in a variety of ways. • They can be carried by water or by the wind.• Animals can move seeds from place to place.• Animals can eat seeds and as the seeds pass

through their digestive system they deposit them in a new location.

ANIMAL EGGS

• Animals reproduce sexually. They begin as fertilized egg cells that develop into embryos. • Some mammals lay eggs as well as most fish and

amphibians.• Fish and frogs lay their eggs in water. The water

keeps the eggs moist and a jellylike layer protects the embryos. Food is provided for the embryo from the yolks of the eggs.

ANIMAL EGGS

• Reptiles and birds have eggs with a tough shell and liquid inside for protection. The tough shell allows them to lay their eggs on land. The yolks inside provide food.• Most mammals develop inside their mother. They

get nutrients from their mothers’ bodies as they develop. Monotremes are the only mammals that lay eggs. All other mammals give birth to live young.

WHAT DO ALL SEEDS NEED TO GERMINATE?

• Water• Soil• Warm temperatures

WHAT DO YOU THINK IS INSIDE SEEDS?

• No matter what size the seed is, they all contain a small embryo plant surrounded by a food supply.

• Why do you think seeds have a seed coat?• To protect them

WHAT IS THE FUNCTION OF THE FRUIT?

• It protects the seed.

HOW DOES A BIRD’S EGG PROTECT THE EMBRYO DEVELOPING INSIDE?

• The shell keeps the embryo from drying out. The yolk provides food for the developing embryo.

SEED COAT

• What do you wear to protect you from cold, wind, rain, or snow?• A coat

• Just like your coat protects you, the coat on a seed protects the seed from the environment.

HOW IS A FISH OR AN AMPHIBIAN EGG PROTECTED?

• By a jelly-like layer that surrounds the egg.

Fish Eggs Frog Eggs

GERMINATION OF A SEED

• Describe the sequence of events that lead to the germination of a seed.• A seed is produced. The seed develops and falls

from the parent plant. Wind carries the seed to a new location. The seed will germinate if conditions are right for growth.

• A volcanic island in the ocean has no plants growing on it. Soon seed plants appear. How might these seeds have reached the island?• Seeds could have blown there with wind, floated there as fruits or seeds in the water, or been carried there by animals.

• Yeast are fungi that reproduce through budding. Other fungi can reproduce asexually by producing spores. Some fungi also reproduce sexually.

• Budding begins when a small growth, called a bud, forms on the parent cell. As the bud grows, the nucleus in the parent cell divides in two. Each nuclei has identical genetic information. On of the nuclei becomes part of the developing bud and eventually the bud breaks off and lives as a new organism.

MULTICELLULAR FUNGI

• Can reproduce asexually. • Made of tiny filaments called hyphae. Hyphae

tangle together to form a thick mass called a mycelium. When the mycelium breaks off from a fungus asexual reproduction can take place. This could happen if an animal digs in an area. If the mycelium lands in a location suitable for growth, it can grow into a new fungus.

MUSHROOMS

• Have you ever seen mushrooms growing on the ground?

• The mushroom is the reproductive structure of the fungus growing from the mycelium in the soil below.

• This structure, the mushroom, is called a fruiting body.

• Fruiting body: fungal structure that produce spores.

• Spores can grow into new fungi. Spores are a reproductive cell that is produced through cell division. Fruiting bodies can produce millions of spores.

SPORES

• Sporangia: The spore-producing structures of some fungi such as on black bread mold.

• Once the spores are fully developed, they are released. If they land in a favorable environment, theyc an produce new hyphae that can form a mycelium.

• Most fungi can produce trillions of spores. • Spores can reach new places by being dispersed by the wind, water,

or even animals.• Fungal spores can be found everywhere. • Most fungi can also reproduce sexually. Sexual reproduction occurs

when two hyphae fuse and form a new spore-producing structure.

HOW DO SEXUAL AND ASEXUAL REPRODUCTION COMPARE?

• Asexual reproduction is convenient. An organism does not have to depend on another organism to reproduce. It can live in isolation.

• Sexual reproduction promotes variety in a species. It can give rise to offspring better suited to environmental changes. Offspring are not identical to either parent. Some are smaller, larger, or faster.

• The ability to run fast is an advantage for some organisms such as mice. Slower mice are more likely to be captured and eaten by other animals. Over time, fast mice will reproduce and pass on this trait to their offspring.

WHAT IS A SPORE?

• A reproductive cell that is produced through cell division. When conditions are right, a spore can produce a new organism.

WHAT ARE FRUITING BODIES?

• Reproductive structures of some fungi that produce spores

HOW ARE MUSHROOM SPORES DISPERSED?

• Some spores are dispersed by the wind; others are dispersed by insects.

HOW CAN MOLD SPREAD ON A PIECE OF BREAD THAT IS IN A SEALABLE BAG?

• The mold that is on the bread produces spores. The spores can land on other sections of the bread and grow.

STINKHORNS ARE FUNGI THAT SMELL LIKE ROTTING MEAT. HOW COULD THIS CHARACTERISTIC HELP

THESE FUNGI DISPERSE THEIR SPORES?

• If a stinkhorn fungus smells like rotting meat, it may attract insects. When an insect comes in contact with a stinkhorn fungus, the spores may stick to it. The spores may be dispersed in a new location when the insect flies away.

HOW CAN YOU TELL THAT THESE PUPPIES ARE NOT THE RESULT OF ASEXUAL REPRODUCTION?

• The puppies all look different, which means they have traits from both parents. They are the result of sexual reproduction.

DESCRIBE THE SEQUENCE OF EVENTS THAT COULD HAPPEN TO A MOUSE POPULATION IF ORGANISMS

THAT EAT MICE MOVED INTO THEIR HABITAT?

• Organisms that eat mice appear. The slow mice get eaten. The fast mice survive and reproduce. The mouse population then changes to mostly fast mice.