GRADE 7- SCIENCE

HAND Out #1 (CHAPTER 6)

I- REPRODUCTION

 

Reproduction is the process by which organisms produce offspring. There are two types of reproduction: asexual and sexual reproduction.

 

ASEXUAL REPRODUCTION

·         It  does not involve the union of gametes or sex cells. It is the formation of new individuals from the cell(s) of a single parent. The new individuals formed are exact genetic copies of the parents. This method is very common in plants,fungi and microbes.

SEXUAL REPRODUCTION

·         It involves the union of gametes or sex cells. He gametes are the sperm and egg are both haploid. During fertilization, these gametes unite to form a diploid fertilized egg called zygote that possesses a unique combination of characteristics from the sperm and egg.

 

II-  REPRODUCTION IN PLANTS

 

ASEXUAL REPRODUCTION in FLOWERING PLANTS

 

a.       Natural Vegetative propagation

·   A process of growing new plants from plant parts. Only one plant is involved and the offspring is genetically identical to the parent.

 

Parts of plants use in vegetative propagation:

 

1.        STOLON/RUNNERS

2.       Leaves

3.       Bulbs

4.       Rhizomes

5.       Tuber

6.       Suckers

7.       Corm.

 

B- Artificial Propagation Methods

Artificial propagation means that part of a plant is cut off from its parent and treated so it grows into a new plant. This method is quicker than waiting for seeds to be formed and germinate. All the new plants produced by artificial propagation will be exactly the same as the parent.

1. CUTTING

Any portion of a plant, a piece of stem ,leaf or root ,which has been removed from a plant with the object of inducing it to strike roots and thus begins an independent existence.

2. GRAFTING and BUDDING

·         It is an operation in which two cut surfaces of the same or different plants are so placed as to unite & grow together. The plant on which grafting is done is called stock & the plant part is inserted on a stock, is called a scion or the graft.

 

 

 

 

 

 

3. Layering

·         a process whereby a shoot of the parent plant is bend until it can be covered by soil.

 

 

SEXUAL REPRODUCTION IN FLOWERING PLANTS

 

All flowering plants reproduce sexually, which involves the fusion of sex cells from parent plants. Sexual reproduction happens in the sexual organs of flowering plants. Most plants are hermaphrodites, which mean that each flower has both male and female sex organs.

PARTS OF A FLOWER

MALE REPRODUCTIVE ORGANS

1. Stamen- male reproductive part
2. Anther- produces pollen
3. Filament

FEMALE REPRODUCTIVE ORGANS
a. Pistil- female reproductive part

2. Stigma
3. Style
4. Ovary- contains the female sex cells called the ovules

 

 

 

 

STAGES OF SEXUAL REPRODUCTION IN PLANTS

1. POLLINATION

Types of Pollination:

a.       Self Pollination
Transfer of pollen grains from an anther to the stigma of the same flower or to a flower on the same plant is known as self-pollination.

b.      Cross-pollination

Transfer of pollen grains from the anther of the flower on one plant to the stigma of the flower on another plant

2.       FERTILIZATION

3.       SEED DISPERSAL

4.       GERMINATION

 

III-                REPRODUCTION IN ANIMALS

ASEXUAL REPRODUCTION IN ANIMALS

 

a.       FISSION

·         An process wherein the organism divide into two (binary fission) or into many fragments (multiple fission) and the pieces develop into new individual which are the exact clone of the parents.

b.      FRAGMENTATION

·         Involves the breaking of any part of the body or breaking up the entire body into several pieces. The broken parts in time develop into complete new individuals.

·         It is complemented by the process of regeneration.

c.       BUDDING

*     A process wherein new individual is formed through formation of a bud, which in time splits off from the parent and develops into new individual.

d.      SPORULATION

 

SEXUAL REPRODUCTION IN ANIMALS

 

The primary goal of sexual reproduction is to merge the sperm cell and egg cell to make offspring. This process is called fertilization.

Types of fertilization:

·         External Fertilization-Fertilization that takes place outside the body

·         Internal Fertilization-Fertilization that takes place inside the body of the female.

HANDOUT #2(CHAPTER 7)

Ecological Way of Life

 

ECOLOGY

·         A branch of science that deals with the study of interactions and relationships of living things with one another and with their environment.

·         It comes from the Greek word “oikos” which means house and “logos” which means to study.

 

Layers of Ecological Organization:

 

a.       Biosphere

*        The part of the earth that supports life.

b.      Ecosystem

*        It is composed of all living things interacting with one another and with their environment.

c.       Community

*        Consists of different species of organisms that interact with each other in a given area.

d.      Population

*        A group of organisms of the same species that lived in a defined area,

e.      Habitat

*        The actual place or type of environment in which an organism or population lives

 

ECOSYSTEM AND ITS COMPONENT

 

A.      ABIOTIC COMPONENT

*        The nonliving chemical and physical factors that help sustain life in the ecosystem.

*        It includes: soil, sunlight, temperature, air, inorganic nutrients

B.      BIOTIC COMPONENTS

*        Is made up of two groups of organisms; those that can produce their own food and those that consume or eat other organisms

a.       PRODUCER/AUTOTHROPHS

*        The only organisms capable of utilizing the energy of the sun and incorporating it into organic material (starch) through photosynthesis.

Examples: flowering plants, trees, photosynthetic bacteria

b.      CONSUMERS/HETEROTHROPHS

*        Organisms obtaining their nutrients and energy by subsisting on other life forms- animals, fungi, bacteria

a.       Herbivore

b.      Carnivore

c.       Omnivore

d.      Scavenger

e.      Parasites

c.       DECOMPOSER

*        Organisms that convert organic matter into inorganic material- fungi, bacteria, some insects, worm

 

 

 

 

 

 

 

 

 

 

 

 

 

ENERGY FLOW IN ECOSYSTEM

 

a.       FOOD CHAIN

*        the sequence of who eats whom in a biological community (an ecosystem) to obtain nutrition. 

In a food chain, energy is passed from one link to another. When a herbivore eats, only a fraction of the energy (that it gets from the plant food) becomes new body mass; the rest of the energy is lost as waste or used up by the herbivore to carry out its life processes (e.g., movement, digestion, reproduction). Therefore, when the herbivore is eaten by a carnivore, it passes only a small amount of total energy (that it has received) to the carnivore. Of the energy transferred from the herbivore to the carnivore, some energy will be "wasted" or "used up" by the carnivore. The carnivore then has to eat many herbivores to get enough energy to grow.

Because of the large amount of energy that is lost at each link, the amount of energy that is transferred gets lesser and lesser ...

*        The further along the food chain you go, the less food (and hence energy) remains available.

*        Most food chains have no more than four or five links

*        A change in the size of one population in a food chain will affect other populations.

 

 

Trophic Levels:
The trophic level of an organism is the position it holds in a food chain.

1. Primary producers (organisms that make their own food from sunlight and/or chemical energy from deep sea vents) are the base of every food chain - these organisms are called autotrophs.
2. Primary consumers are animals that eat primary producers; they are also called herbivores (plant-eaters).
3. Secondary consumers eat primary consumers.  They are carnivores (meat-eaters) and omnivores (animals that eat both animals and plants).
4. Tertiary consumers eat secondary consumers.
5. Quaternary consumers eat tertiary consumers.

Food chains "end" with top predators, animals that have little or no natural enemies.

 

 

 

 

 

 

 

 

 

 

 

 

 

b.      FOOD WEB

*        Describes the feeding relationship of organisms in an ecosystem. It shows how a variety of food chains are interrelated with one another.

 

 

 

 

 

 

 

 

 

 

 

 

INTERACTIONS IN AN ECOSYSTEM

A.      INTERSPECIFIC RELATIONSHIPS

-    Exists when two different organisms interact together. Examples of these interactions are symbiosis, predation, interspecific competition.

A.      SYMBIOSIS

Symbiosis is a term used to refer to any intimate or close association of two organisms of different species. Symbiosis (from the Greek sym “together” and bios “life” literally means “living together”. In any symbiotic relationship, at least one of the participating organism is always benefited and the other may be harmed, not affected or benefited also. Hence, symbiosis can be classified as:

 

a.  MUTUALISM- both organism benefit from each other.

Ex: coral polyps and algae, flowers and bees

b.                        COMMENSALISM- one organism (the commensal) benefits while the other organism (host) is neither helped nor harmed.

Ex: Epiphytes growing on the trunk of a tree, sharks and remora

c. PARASITISM- one organism (the parasite) benefits while the other organism (host) is harmed.

Ex: Parasitic worms which live and derive nutrition from their host, dog and tick

 

B.PREDATION

A relationship where one organism attacks kills and feeds on another, the organism that attacks and kills is called the predator and the organism that is killed is called the prey.

                       Ex: An eagle preying on a rat, hawks eat snakes

 

C.INTERSPECIFIC COMPETITION

A competition between organisms belonging to different species

                       Ex: Competition for sunlight in a forest

 

 

B.      INTRASPECIFIC RELATIONSHIP

-It involves interaction of organisms belonging to the same species.

        INTRASPECIFIC COMPETITION- a competition between organisms belonging to the same species.

Ex: competition among bats for fruits